Two male rabbits getting along?

Hi

A 9 week old baby rabbit accidentally got into my 3 year old male rabbits enclosure. I was really surprised, because the rabbits were getting along so well. The rabbit have been sharing a wall the whole summer, so they have been able to sniff each other through it, which might explain a little why they get along this well.

I always wanted to get my male rabbit a friend, but I was told that my rabbit could not be neutered the usual way, but he would need a surgery, which would be dangerous. And I know that bonding two male rabbits can be very difficult.

I was planning to ask the owner if I could buy the baby rabbit, if it actually does get along this well with my older male rabbit.

So I was wondering if my male rabbit is only being this accepting towards the other male rabbit, because the other one is still so young? Would it be likely that the rabbits would become more hostile towards each other once the other one gets older?

Any help please