How Can I Be A Better Sister?

I have a younger half brother (our ages are pretty apart). I’m female btw. He’s in college now. So we have the same father but he passed away 4 years ago. My brother also has other half brothers who I’m not related to, but who love him equally as much.
It was hard for me to communicate with him when he was younger but my father would always keep in touch with me to let me know how he’s doing, etc. and although I hardly spoke to my brother when he was younger I visited him probably every 4 years. And every year I would buy a birthday card for him but for some reason would be unable to send it, so anyway he’s the one who e-mailed me to let me know that my father had passed. Btw We both live in different countries. So I traveled there to go to the funeral and at that time I never claimed my inheritance and left it for my brother and his family. And my brother did talk to me about school and etc. and I was happy, but I was so horrible at showing affection. His half brothers were there also and I’m not so sure they like me although I have nothing against them.
So anyway, my brother and I keep in touch via Facebook now but I noticed that he’ll only respond to me when I private message him (he usually responds really quick). He won’t respond to me when I comment on his wall or anything, but he will wish me happy birthday on my wall every year. As I’m growing older I sometimes wish I were close to him, but I also understand that I wasn’t all that there when he was younger either.
I also wish him happy birthday each year and this year I plan on sending a t-shirt. I’m not sure what else I can do to be closer to him. Also, I’m waiting for him to be z bit more older so I can ask him what actually happened to my father.
I’m wondering if he actually cares and what I can do to be a better sister, or is what I’m doing enough? I know he’s in college now and probably busy with his social life as well, so I’m just being patient now.