How would you deal with this family drama?

Tweet

A friend's nephew, in his late 20s, appears to have become delusional, and it's affecting his whole family. Or maybe he's just a compulsive liar. But it's still affecting his whole family. When his cousin, a young woman of about 20, got into UC Berkeley, he suddenly claimed to have gotten into Stanford Graduate School, in Physics, based on a paper he wrote at a Community College. I read the paper, and it was drivel. Recently, his father died. He claimed that a "huge grant" he'd gotten at Stanford would save his mother's house. When no money appeared, he blamed his cousin, the one who had gotten in to UC Berkeley. He said she was on a terrorist watch list, and that this had cost him his grant at Stanford, or something along those lines. His mother is in denial. She believes his whole story. My friend (the brother of both mothers involved) and his wife know it's BS, but don't know whether to intervene. The mother of the UC Berkeley young woman, and sister of the lying young man's mother, doesn't know what to do. Everyone is afraid to confront the young man's mother, because she's still grieving the loss of her husband. Many tears have been shed. I have been shown some of the "acceptance letters" and "recommendations" the young man ostensibly received from Stanford. They read like something cut and pasted from the internet and "tweaked" by Community College student who lacks writing skills (because that's what they are). Obviously, an intervention is necessary. But who should do it? Note: The photo is of a broken corner I'm fixing on a pair of JBL L-100s. Fixing a broken corner is easy. Fixing broken families is hard.