Teenage boy doesnt' act like the average boy?

I know that everyone is different and some children mature faster than others, I am so concerned about my nephew. He is 13yrs old, a few months ago my sister and I found out he had been browsing gay sites, every since than we have reached out to him let him know how much we care about him and love him, he says that he's not gay and he dont know why he was going to those sites (at this age I know he maybe confused and not really know what he is) I'm just concerned about him, he doesnt play in sports nor watch any sports at all, he loves to dress like young boys with the latest styles and such things yet I'm just confused by some of his actions. He's not real feminine or anything but he's not manly either. I am just wondering is he going through a phase or what, we try to enroll him in summer programs etc, to get involved in sports or to just have a life but he's never interested in anything, he doesnt come from a bad home, we've talked about school and whether or not children may be bullying him and he says no he's ok at school. So I dont know what to do or think my sister is a single parent and it saddens me to see her wondering and worried about her son because he's just not socialable around other people outside of our family members or children at his school this is not good for a 13 year old boy.