This reminds me of my entire childhood. Mom got in trouble, my 2 siblings and I briefly went into the system until my newlywed grandma got custody. Her husband didn’t want us so he ended up treating us like live-in cleaners while making my grandma (who made less than him) pay for anything having to do with the three of us. She was a wonderful woman who loved him (and his children and grandchildren more than he ever did) much more than he deserved. NTA but I’ll give you the advice I wish my grandma had listened to: leave him. If he can’t even muster the decency to care about feeding a child in his family, he’s not someone who deserves a special place in your life