Why does she keep bringing him up?

So my friend who is a year younger than me has a brother my age, and i think he started to like me because he was always looking at me, getting nervous, flirting with me over aim etc. But then he found out i liked him and said he didn't feel the same way, yet he would always look at me, and get nervous around me. But it seems that everytime me and his sister gets together to go to the pond or hang out she always ends up mentioning him like "yeah he can throw a baseball really far, it would have gone farther but it hit the fense" and when i started talking bout nascar she goes "geez you and him have soo much in common i can't believe you don't like him, i should hook you guys up," or when i said i was a picky eater she said "hes a picky eater to you guys complete each other." so how come she keeps doing this, i don't understand. why everytime her bro comes up in a conversation.