1 of my 3 kittens went in2 heat, but unlike the other 2 she dsn't use the dog door. Since she started, will the others?

cats are seasonal ovulators --- they come into heat in the spring if they are old enough --- if all these kittens are related ( the same age ) then the other 2 will be coming into heat soon just like the sister

We wish to as soon as possible, but we can't do it for at least another few weeks. i'm worried because although the other 2 aren't showing signs, since Blue is in heat i'm afraid she's already attracted a male cats attention and he's been hanging out on my porch for the past few nights and the two kittens are taking interest. So I was wondering if it's like women. When one starts then the rest in the house start?

Look into low cost spay and neuter programs in your area and get it done, PLEASE. Get them all done.

I will as soon as i am able to. I do not wish to have any more kittens especially since the ones I have are still kittens and the costs are not at all an issue. I just needed to know if i should start preventing the other two from going outside as much as possible until I can get them spayed even if they don't seem to be in heat like their sister who stays inside.

Yes, keep them all in until they've had surgery and healed.

Okay, thank you

Wow. Okay, thank you. I obviously know nothing about cats and I deeply appreciate the information :)