Generally, opposite sex pairs are easiest to bond. Of course they both should be spayed or neutered. Same sex pairs can work, but it is a bit more tricky, generally 2 females tend to be easier than 2 males. Of course, it really does depend a lot on the individual rabbits and their personalities and not as much on the sexes.
If your rabbit is a female, then I would recommend looking at a male, but also be open to a female.
Babies can be iffy. You don't really know what their personality will be like and they can change as they become adults and hormones come into play. You may need to wait for the younger one to mature more and get neutered before you can have them live together.