stupid question about heat

I have two black female kittens that are almost 7 months old. They have not been spayed yet, but will be soon. How do I know if they have had a heat cycle. They haven't acted like it, but they are definitely old enough to have had one. Are some cats just late bloomers? My other adult female also soon to be spayed has a silent heat, but I know she is in heat cause she tries to get outside and that's the only time she does it. Are there other signs I should be looking for?

Yes, some shecats have silent heat, like your other female. But fertile he cats of course know... And some neutered too. If you have some such in neighborhood you can use it as a try-out....

A good test is to touch them at the tails root. If they in heat they will show it at once by crouching down, tail aside, behind up and working with the behind paws...

Other shecats do it more openly: they wants to be petted a lot, they meows a lot, they can disbehave at the most inapropriate places - althought they othervise are perfect with the litter. they can yell. They can trash around like very sick... And they want out yes.

Not all cats do get in heat at 6-7 month or earlier. Many does it later too

It wasn't a stupid question.

Yeah there are some tomcats around they belong to my neighbor. The black kitties don't pay attention to them yet, which is a good sign I guess. My other cat is very funny about it... she yowls for the orange tabby (the father of her litter was also an orange tabby) , but for the white ang grey male she hisses and growls and doesn't want him around, apparently I have a picky girl. Has anyone else ever experienced that?