A bird who has basically been a single bird for most of his life may not want to be friendly with another bird. If that's the case you can keep them in separate cages, or keep them in a very large cage where they have plenty of room to put space between themselves. They will form a flock bond in any case, and won't want to be too far apart even if they also don't want to be too close together. They may not want to be in the same cage but they'll want to be in the same room.