Should we be worried about my male cousin's um, hobby? Barbies?

I have a 13 year old cousin and he told me about this weird thing he does. He gets dolls like Barbie, Ken, GI Joe, etc, usually from thrift shops and yards sales but sometimes new ones. He alters their appearance to look like his school friends like he changes hair and outfits and stuff. Then he gets bodily "stuff" from these people like collects their hair and some he gets to give him blood I don't know how. He has one barbie that he says looks like his female friend and she cuts herself so she gave him a whole vial of blood. Then he took her blood and put some inside the barbie (he took it apart and hollowed it a little). He does that with all the blood, hair, etc he gets - hollows the doll and puts it inside.