I started out with 2 queens that were no more than house mates, they tolerated each other, but no more, though they had been together for 4 years before they came to live with me.
When they got too old to defend their own garden, we got 2 young toms, who got on like a house on fire, though 1 was 5 years old and the other 6 months, and especially the younger one was very sweet to the girls.
When the forst old lady died, we introduced a semi feral 18 weeks old, Tosca. Again, the girls tolerated each other, and she became friends with teh boys in no time. When the younger tom got run over, Tosca was devastated, and we took in a rejected tom who was the same age as Jiskefet when he died. Again, the males and Tosca were fine with each other, and Steffie, my senior queen, gracefully accepted the friendliness of the toms, without actively befriending them.
We then got a very old, very dominant queen, who 'could not stand other cats'.
Well, she lived here for 2 years before passing away. The others respected her dominance and kept clear of her, and all was well. She even tought all my other cats not to be afraid of fireworks.
When Steffie died, we got a tiny, very macho tomcat, who ruled outdoors while old Precious ruled indoors.
After Precious died, Spetter, the tiny macho, kept the whole bunch in check. The 3 toms were brothers in crime,outside, they were always together.
We inherited 2 queens, one of which died soon after her slave, unfortunately, she turned out to have FIP, which was probably activated by the stress of her slave dying. But the other one, Josje, settled in quite well, though she seemed a little lonely. Again, she did not have the connection with the toms, though they were friendly enough.
We took in one more adult tom, who turned out to be too scared of people ADN other cats, and felt so threatened that he attacked all the other cats. So he was sent back to the rescue, he simply did not fit in with the other cats at all. There was hairs and blood all over the place, and Josje lost weight rapidly, due to stress.
Then we took in another adult tom, about the same age as the previous one, a stray, who keeps himself more to himself, and doesn't seem to care much for the other cats. But this time, there were no major problems, just a bit of hissing. This cat is rather dominant, but Tosca and Xena are a match for him, so it is more or les a joint leadership with mutual respect.
We also introduced 2 kittens in 2 years, first a queen (Xena, now 2 years old) and then a tom (Gaudi, now 16 weeks old).
Both were fully accepted by all, and even Josje is a lot closer with them than with the other cats.
So if you want them to bond, I suggest a young tom, no more than 4 months old, would be best.