Generally speaking I would say you shouldn't ever ask for a gift to be returned. Not a good look.
However, in the case of your brother, I would say it depends on the kind of relationship you two have. If you're super close, have no secrets, can talk about anything, and bust each other's chops without anyone getting offended I would say you could ask for it back. Maybe start off by giving him a hard time about not using it and see where it goes. Who knows, maybe he wants to get rid of it and is only keeping it because you gave it to him.
However, in the case of your brother, I would say it depends on the kind of relationship you two have. If you're super close, have no secrets, can talk about anything, and bust each other's chops without anyone getting offended I would say you could ask for it back. Maybe start off by giving him a hard time about not using it and see where it goes. Who knows, maybe he wants to get rid of it and is only keeping it because you gave it to him.