So I was fighting some mobs while i was exploring and I came across a skeleton. It dropped a weird bow. The reason why its weird is that it has unbreaking 1 and unbreaking 2 at the same time!

.....

I wonder if you can upgrade it to unbreaking 3 without losing the unbreakinv 2 as well

Sadly its turns into only unbreaking 3

You can get these from skeleton trap guys fairly rarely :)

i got something like that too

If you were to enchant it with another Unbreaking I book, would it turn into Unbreaking III or just Unbreaking II or two Unbreaking II?