Is this normal for a 15 year old dude?

okays so about 1 year ago we got 2 member in our family. my moms sister is crazy and got arested and got in jail for like 23 years or somthing.... so now we have her 2 twin boys live at the house. they are the only two guys in the house besides my dad, but hes a doctor so hes not around a lot. but anyways one of the twins are cool he will talk to us he has warmed up to us all preaty quick. but the other one is odd. he is really quit, doesnt talk to us much, and jsut listens to his i pod a ton! so clearly he loves music. like for chrismas everyone asked for stuff, even his twin and all he asked for was i tunes gift cards. and at school i see him a lot but he jsut hangs out with his group of friends.the only time i ever heard him talk really loud was when his friend from where he used to live came and visisted. i could hear him having yelling and having fun, and playing black ops and all that from my room. and the weirdest thing was the whole familly left one morning when he was still sleeping and when i came home i could hear him playing our drum set downstairs, he was REALLY good!! it was amzing!! i feel really sorry for him!! what should i do? should i do anything? he doesnt do the whole conselor thing BTW lol, o an btw im putting this in womens health cause i thought you guys would know best lol and also he has a gutair i have heard him play a couple of times.... he is a really goood! i am picking him and only him up from school tomarow.. should talk to him?? cause he will have is i pod! haha and idk about black ops and drums and all that so idk what to talk about. and we do include him in our family.