sex

Question
My male rat terrier (I call him a BRAT terrier) has been neutered for about 4 years. I have two 9 month old Chihuahuas (sisters) when is in heat. (waited to long to get them spayed)  This morning found the male and female attached. There have been incidents of him trying to hump her but I have been able to keep them apart.  Besides I thought it was just a dominance thing. Do I have to worry? I'M I going to have oops a puppies?  Is this normal behavior? Can a neutered male still attach? Thank you
Is this normal

Answer
Yes neutered males can attach. No they cannot have puppies as long as his surgery was normal and he didn't have any retained testicles that were not removed.
It isn't a dominance thing as much as a hormonal. Our biggest sex organ is our brains, same with dogs to a point.
Get them spayed as soon as the swelling is down in their vulvas or some other dog will OOPS them!

Just for the record, I had a gelded horse thirty years ago that bred a young filly we had. No foals, just had it in his brain he could do it and he did.
So it happens with most species (except maybe cats).