You can get two kits, but you’d have to separate them at about 12 weeks if they are boy and girl, a bit later if they are the same sex. Boy and girl can get babies, same sex bunnies esp male bunnies, will get into fights when they become sexually mature. You should never let them “fight it out” – they can hurt each other severely and they can bear a grudge if they have gotten into serious fighting.
After you separate them, (it’s best to let them live in the same room so they can see and hear and smell each other) you have them de-sexed at the appropriate age (for boys as soon as the testicles drop, for girls around 6 months). You let them heal for a month, allowing time for the hormones to die down completely. Then you start rebonding and that’s often successful if they had a good relationship before they were separated.
Another option would be to raise the little one you’ve bought, have him/her desexed, and then try to find a friend for your bun, preferably by doing bunny speed-dating at a shelter. If the buns can choose their partner themselves, bonding will be much easier. Us humans can have no idea what attracts two bunnies to each other, it probably has to do with body scent and body language, i e subtle things that we can’t perceive.