Hi...

I have two neutered dogs and a 20 week old puppy bitch.....she has just been to the vets and she has got Juevenille vaginitis...........the vet sais I should have her speyed now untill she has had her first season.... I was planning on having her done at six months.....

Just wondering how my two dogs will deal with the situation......is it likely they might become aggresive with each other because she is in season?

I guess all I can say is that it depends on the dogs. I know some dogs that have totally lost interest once they ahve been done. Unfortunately mine is not one of those and gets very protective of her and agressive towards other dogs, so we have to do our best to keep them apart. 

Ahh , my late american bulldog bitch had great fights with my late GR bitch. I think two bitches in season are bound to fight.

I had two dogs fighting when my bitch wasn't even in season! but constantly after her attention (she was top dog).
It depends on the dogs mine would fight but not seriously and quickly forgotten.

At one time I've had 3 bitches 2 of which cycled within a week of one another and the
third followed a month after.
No fights then. Now I only have two of the three entire and still no fights.
My breed is Boxers.
I can even allow all three to have bones together, no problems.
My oldest bitch is 7yo, the middle one her daughter is 4yo and the youngest
whom is a cousin of the 4yo is now 19 months old.

We have gotten off track here a bit folks :D  the original poster needs to know if his two castrated males will fight while the bitch is in season.

Depends on the dogs

When our GSD bitch had her season we had 3 entire dogs & no problems but & it's a big but the bitch was well kept away from the dogs from day one & two of the dogs were at work with me 24/7 so had little contact with her until she had finished her season & been bathed

I had two dogs who got along fine, until I introduced a spayed bitch - so it really does depend on the dogs - there is no definitive answer I'm afraid :(