Speaking from experience, this sounds like a very entitled sibling who has always gotten what they wanted from parents (my ungrateful older brother).

Kind of was in the same position as you in the past OP. I footed half the schooling bill for my niece and It’s because I love her to bits. Once I was trying to save up and move forward in my life with my at the time girlfriend, he threatened to go NC when I said I couldn’t pay for her education. Granted I’m 7 years younger than my brother and I was busting my ass with work. I know (never expected) that my selfish older brother wouldn’t lift a finger to help me with my kids in the future. I was right in my assumption.

Anyways, he went NC for about a year and then he reaches back out to amend our relationship. I obliged and met up with him and guess what? He asked me for 100k this time. Didn’t care to ask anything about my family or even show up to my wedding (I invited him to every major event regardless of his choice being NC). So yeah, long story short, I do not regret going NC. He is family and blood but he’s practically an entitled grown child and he’s got to learn how to survive.