Male kitten with older male cat

A lady(and her husband) would like to adopt one of my kittens (male because our litter consists of 3 males and 1 female) . They already have a 5 year old male cat (neutered).

Is this OK? Or will male cats only accept females? (the cats are my boyfriend's and I'm asking him on behalf. I've ever only had hamsters and older male hamsters generally don't accept baby male hamsters)

Male cats are fine with other males, so long as they are neutered. Whether this lady's existing cat will accept a newcomer will depend more on the purrsonalities involved than whether it's male or female. I've recently introduced a male kitten to a 9 yr old male (8 at the time of introductions) and they've been fine

It actually depends more on the personality of the resident cat. Kittens are usually pretty friendly with everybody and everything. I rescued 5 kittens and Wawa (my neutered boy) accepted them immediately. The rest of the gang (spayed females) took a much longer time liking the little ones.