The time and patience is needed in any case. Filou and Tigris came together when they were 13 and 16 weeks old. It took one week before they stopped to ignore each other. THen they hissed and growled. And they were inseparable then.

If you bring cats together, they won't be friends after an hour. Which doesn't mean they won't be friends.

The kitty is incredibly sweet All the best.