I am extremely close to my Big Brother! I wasn't 100% sure when I picked him as a Big (but how can you be after only 8-10 weeks?!), but I am incredibly glad that I did. I love spending time with my Big.
I'm also very close with my twin and triplet (my Big Bro's other two Littles). We have a funny relationship. We're a big dysfunctional family, though.
I'm not as close with my Little Brother, sadly. I did spoil him when I received him, but he transferred to another school after his first semester, so we don't keep in contact as much. I do love spending time with him, though, when he visits and I'm also a little honored that he calls me his older brother instead of his big brother.
When it comes to unofficial relationships, I'm super close to my Big Sister, her Little Sister, and her 3 other Little Brothers (I lived with one for a year and we're all SigEps).