Example of generational curse. The first scripture(2 Samuel 12:1-15 is the cause)
Sorry it's long...it's the scriptures, not my commentary.

After David slept with Bathsheba and killed Uriah...
2 Samuel 12:1-15
1And the LORD sent Nathan unto David. And he came unto him, and said unto him, There were two men in one city; the one rich, and the other poor.
2The rich man had exceeding many flocks and herds:
3But the poor man had nothing, save one little ewe lamb, which he had bought and nourished up: and it grew up together with him, and with his children; it did eat of his own meat, and drank of his own cup, and lay in his bosom, and was unto him as a daughter.
4And there came a traveller unto the rich man, and he spared to take of his own flock and of his own herd, to dress for the wayfaring man that was come unto him; but took the poor man's lamb, and dressed it for the man that was come to him.
5And David's anger was greatly kindled against the man; and he said to Nathan, As the LORD liveth, the man that hath done this thing shall surely die:
6And he shall restore the lamb fourfold, because he did this thing, and because he had no pity.
7And Nathan said to David, Thou art the man. Thus saith the LORD God of Israel, I anointed thee king over Israel, and I delivered thee out of the hand of Saul;
8And I gave thee thy master's house, and thy master's wives into thy bosom, and gave thee the house of Israel and of Judah; and if that had been too little, I would moreover have given unto thee such and such things.
9Wherefore hast thou despised the commandment of the LORD, to do evil in his sight? thou hast killed Uriah the Hittite with the sword, and hast taken his wife to be thy wife, and hast slain him with the sword of the children of Ammon.
10Now therefore the sword shall never depart from thine house; because thou hast despised me, and hast taken the wife of Uriah the Hittite to be thy wife.
11Thus saith the LORD, Behold, I will raise up evil against thee out of thine own house, and I will take thy wives before thine eyes, and give them unto thy neighbour, and he shall lie with thy wives in the sight of this sun.
12For thou didst it secretly: but I will do this thing before all Israel, and before the sun.
13And David said unto Nathan, I have sinned against the LORD. And Nathan said unto David, The LORD also hath put away thy sin; thou shalt not die.
14Howbeit, because by this deed thou hast given great occasion to the enemies of the LORD to blaspheme, the child also that is born unto thee shall surely die.
15And Nathan departed unto his house. And the LORD struck the child that Uriah's wife bare unto David, and it was very sick.
2 Samuel 13:1-20 is the effect. The generational curse.
1And it came to pass after this, that Absalom the son of David had a fair sister, whose name was Tamar; and Amnon the son of David loved her.
2And Amnon was so vexed, that he fell sick for his sister Tamar; for she was a virgin; and Amnon thought it hard for him to do anything to her.
3But Amnon had a friend, whose name was Jonadab, the son of Shimeah David's brother: and Jonadab was a very subtil man.
4And he said unto him, Why art thou, being the king's son, lean from day to day? wilt thou not tell me? And Amnon said unto him, I love Tamar, my brother Absalom's sister.
5And Jonadab said unto him, Lay thee down on thy bed, and make thyself sick: and when thy father cometh to see thee, say unto him, I pray thee, let my sister Tamar come, and give me meat, and dress the meat in my sight, that I may see it, and eat it at her hand.
6So Amnon lay down, and made himself sick: and when the king was come to see him, Amnon said unto the king, I pray thee, let Tamar my sister come, and make me a couple of cakes in my sight, that I may eat at her hand.
7Then David sent home to Tamar, saying, Go now to thy brother Amnon's house, and dress him meat.
8So Tamar went to her brother Amnon's house; and he was laid down. And she took flour, and kneaded it, and made cakes in his sight, and did bake the cakes.
9And she took a pan, and poured them out before him; but he refused to eat. And Amnon said, Have out all men from me. And they went out every man from him.
10And Amnon said unto Tamar, Bring the meat into the chamber, that I may eat of thine hand. And Tamar took the cakes which she had made, and brought them into the chamber to Amnon her brother.
11And when she had brought them unto him to eat, he took hold of her, and said unto her, Come lie with me, my sister.
12And she answered him, Nay, my brother, do not force me; for no such thing ought to be done in Israel: do not thou this folly.
13And I, whither shall I cause my shame to go? and as for thee, thou shalt be as one of the fools in Israel. Now therefore, I pray thee, speak unto the king; for he will not withhold me from thee.
14Howbeit he would not hearken unto her voice: but, being stronger than she, forced her, and lay with her.
15Then Amnon hated her exceedingly; so that the hatred wherewith he hated her was greater than the love wherewith he had loved her. And Amnon said unto her, Arise, be gone.
16And she said unto him, There is no cause: this evil in sending me away is greater than the other that thou didst unto me. But he would not hearken unto her.
17Then he called his servant that ministered unto him, and said, Put now this woman out from me, and bolt the door after her.
18And she had a garment of divers colours upon her: for with such robes were the king's daughters that were virgins apparelled. Then his servant brought her out, and bolted the door after her.
19And Tamar put ashes on her head, and rent her garment of divers colours that was on her, and laid her hand on her head, and went on crying.
20And Absalom her brother said unto her, Hath Amnon thy brother been with thee? but hold now thy peace, my sister: he is thy brother; regard not this thing. So Tamar remained desolate in her brother Absalom's house.
21But when king David heard of all these things, he was very wroth.
22And Absalom spake unto his brother Amnon neither good nor bad: for Absalom hated Amnon, because he had forced his sister Tamar.
23And it came to pass after two full years, that Absalom had sheepshearers in Baalhazor, which is beside Ephraim: and Absalom invited all the king's sons.
24And Absalom came to the king, and said, Behold now, thy servant hath sheepshearers; let the king, I beseech thee, and his servants go with thy servant.
25And the king said to Absalom, Nay, my son, let us not all now go, lest we be chargeable unto thee. And he pressed him: howbeit he would not go, but blessed him.
26Then said Absalom, If not, I pray thee, let my brother Amnon go with us. And the king said unto him, Why should he go with thee?
27But Absalom pressed him, that he let Amnon and all the king's sons go with him.
28Now Absalom had commanded his servants, saying, Mark ye now when Amnon's heart is merry with wine, and when I say unto you, Smite Amnon; then kill him, fear not: have not I commanded you? be courageous, and be valiant.
29And the servants of Absalom did unto Amnon as Absalom had commanded. Then all the king's sons arose, and every man gat him up upon his mule, and fled.
30And it came to pass, while they were in the way, that tidings came to David, saying, Absalom hath slain all the king's sons, and there is not one of them left.
31Then the king arose, and tare his garments, and lay on the earth; and all his servants stood by with their clothes rent.
32And Jonadab, the son of Shimeah David's brother, answered and said, Let not my lord suppose that they have slain all the young men the king's sons; for Amnon only is dead: for by the appointment of Absalom this hath been determined from the day that he forced his sister Tamar.
33Now therefore let not my lord the king take the thing to his heart, to think that all the king's sons are dead: for Amnon only is dead.
34But Absalom fled. And the young man that kept the watch lifted up his eyes, and looked, and, behold, there came much people by the way of the hill side behind him.
35And Jonadab said unto the king, Behold, the king's sons come: as thy servant said, so it is.
36And it came to pass, as soon as he had made an end of speaking, that, behold, the king's sons came, and lifted up their voice and wept: and the king also and all his servants wept very sore.
37But Absalom fled, and went to Talmai, the son of Ammihud, king of Geshur. And David mourned for his son every day.
38So Absalom fled, and went to Geshur, and was there three years.
39And the soul of king David longed to go forth unto Absalom: for he was comforted concerning Amnon, seeing he was dead.
Correlation:
David took another man's wife and forced her. How did he force her? Just by being king, she really had no other choice even if she didn't want to. Because of this, Bathsheba of course became pregnant and in those days would have been stoned if it came out that since her husband was at war at the time that she cheated on him so David sent for Uriah to try to get him to lay with his wife, but since Uriah was such a patriot, he wouldn't go to the luxury of home while his compatriots were off at war so David had to kill him so that he would not bring charge against her. All David wanted to do was sleep with her, had Uriah slept with her, everything would have been fine and no one would have been accountable for their actions.
Amnon lusted so hard after his sister that he forced her to sleep with him, even after she pleaded to him to ask the king (David) if they could marry. And after he got what he wanted he, hated her so much that he sent her away from him. He wasn't interested in marrying her, especially his own sister. This enraged her brother Absalom probably not only because this was his sister, but because Amnon took away her suitability and brought shame on his and his sister's head. Because of that, and the fact that his father knew, but did nothing, he killed Amnon.
Although it doesn't come back on you the exact way you give it out, you get it back twofold. What David did to another family happened all in his own house.
Generational curse, both David and his children were affected by his sin with Bathsheba.
Generational curse doesn't so much mean that if I'm stupid then my children will be stupid without a doubt, it means that in some instances, you will see your sin in your children because a lot of times we don't see our issues until we're looking at them in someone else. That's why people say that if you do a certain thing around a child that they will do it too.
That's just one instance that I could think of right off hand because I heard a lesson on this situation. The person wasn't teaching generational curse, but that's what I got out of it.