I don't see that the small one too thin... I believe that in the real trees, when having more than a trunk, one gets more food than the others, and there's one weak trunk... I believe that it is the way your tree will look... Just a thought, but you need to remove all the lower leaves, and take a far pic (I mean where the whole tree is visible) and if you can a close up one... And if you can try to pick a front, and take the pics from your front... ok? and good luck with your tree
If you do everything as Matt says, you will not only learn TONS, but you will have a nice tree in some years... so, bye