Yep, he's likely a young gander then. If you are looking for a mate, I suggest you find a confirmed female around the same age, maybe younger. If he's a male, then they should be fine. If not then you have two females, which will be fine too. And, if you eventually want to breed, and they are both females, finding a confirmed gander will be pretty easy.
Just take your time introducing them to each other as well as the rest of your flock and they should do OK. He/She really would do better with a mate, whichever way you decide to go.