Thank you both for your help.
I will be home in a week and plan to talk to my sister in law about this then. She tried to talk to her father about it, and he kept interrupting her to tell her how great her half brother is. Subtle.
My father and I have been trying to talk about this too, up until I moved. (He's not much of a phone talker.) His father was a nice old man, but when he was younger he really just ignored his first family. For instance, my grandfather lived in Jamaica, Queens (NYC), and my dad lived in Altamont (about a 3 hour drive on a good day.) So one day when my dad was 19 he hitchhiked to his father's apartment. It took him like 7 hours. So he gets there, rings the bell, and his father yells through the door "Who is it?" My father goes "Your son, ______." My grandfather goes, "I don't have any kids." And wouldn't answer the door.
So my dad hitchhikes home and when he finally gets there, there's a message from my grandfather. He told my uncle (dad's older brother) to tell my father that he was too old for child support and not to come to his house again. My dad had gone down there to tell his father that he was getting married and that my mom was expecting the first grandchild.
So you can see the issues. My grandfather, as time went on, really liked us grandkids, but we still only saw him once a year. He didn't come up to live near us until he found out he was dying of cancer (he died less than a year after he moved.) He never missed a birthday card. But really, he didn't care all that much. He never spelled my name right. He didn't even know my older sister's full name, I don't think - only her nick name. He knew absolutely nothing about us and didn't really ever want to find out.
Oh well. Now I'm sad

My dad is getting better - its been 4 years. My cousin - I hope she gets better. As far as I know she's engaged, so I imagine that will help

We'll see.