We have two small dogs, both same breed, both rescued but at different times, same age (4) but different gender (both neutered) They get on very well together and we love them to bits. We would love to introduce another dog to the family but this is a different breed, same age and male.

Our main concern is, is it wise and would it upset the balance between the two we have? Our boy was the last to join the family and we had no trouble with him but on occasion, while out, if either sees another dog, they will growl and pull towards the other dog, barking. This isnt with everydog but I havent worked out what the difference is. The new dog would be about twice their height!

Until you have sorted out what the reason your two dogs pull towards some other dogs as you have described, I would not reccomend you get the third dog. The new dog would learn this behaviour, and being larger could pull you along with it. Take the dogs you have to a good training club and get them sorted out first.