Don't feel guilty - they won't even miss their missing pieces.
Yes, its necessary for indoor only cats to be neutered. You are going to go crazy if you don't - the cats will spray to mark territory (very smelly, very hard to get rid of), find ways to escape the house in search of females, and all it takes is one escape for your cats to help make kittens. Also with two males, they might start to fight all the time over territory (your house) Since your kittens are so young, they will recover very quickly.
Take a look at the question right after this one titled "Help!! Cat pees EVERYWHERE?" |