Please don't list this on a work's page as a trope. Examples can go on the work's YMMV tab.
Tear Jerker: Maury
One of the saddest examples from Maury came when a fifteen-year-old teen mom was murdered, and an eighteen-year-old man said he thought he was the father, and even wanted to be. He was brought on with the deceased teen's mother and sisters. It turns out he was not the father. On top of that, the only other candidate to be the baby's father was also dead.