@haphazard-hstead
cheers! grafting would definitely be useful!
@opheliafu as what @haphazard-hstead wrote - you could graft a stem of your fruiting apple to that of the one that is not fruiting yet or you could trick it that it is already fruiting by stretching its branches horizontally. Just make sure that there is just one stem leader on top and that the tree have at least a maximum of 8 main branches since they are still considerably young. Cheers to all the apple growers :)