So now one of my father's other kids who's a preteen or something sends me a friend request all like "I am your brother. I want to be friends with you."
Just accept the friend request, put him on a list which grants him no access to your profile, and ignore him til he's 30-40 and less likely to ask for money.
I knew of a half sister that I'd never met. She contacted me via Facebook. I spoke of it here. "Family person" or not, you shouldn't shut them out. Health matters alone is one reason to be curious.
Dear Kidne. . .Sister,
I hope that you are well and drinking plenty of fluids.