after the first flower, biologically compatible mates should ask "try for kits?" at the end of their dialogue when given pink tulips. saying yes will result in a random chance of pregnancy, meaning it'll probably take a few flowers to produce results. if you're female, a kitting countdown will start and you'll give birth in your clan's nursery, but if you're male, you'll have to give your mate another flower for them to tell you they're pregnant, and a bit after that kits will show up in their clan's nursery. there's currently no way to tell your mate has given birth past the first litter unless you go to gatherings, in which case the births will be announced, so you may want to periodically check the nursery. hope this helps