I have a lab and a biewer! I am looking to add a yorkie to the mix
I have had a boston terrier before, great dogs, smart, easily trained and very friendly with other dogs and people, children, etc. Also, a protector, no one would come in the yard without her barking...but she wasnt an excessive barker.
Ive also had an english mastiff, she was a rescue, and very much a gentle giant. No one would think about coming into our yard because she was so big, but she wouldnt hurt a fly. I adopted a kitten and she would just lay there and the little cat would play and bite her. lol
Ive had a pitbull mix who was very friendly with people/children, but not other dogs. She actually lives with my mother in law
And, Ive had a boxer mix. I got him as a puppy when I was 3-4 yrs old, and he lived until I was 16. He got along with all the other pets I mentioned, except the pit, who was adopted after him. He was kind with people, pets, children, everything.
Honestly, I think it depends on the attitude more than the breed. If you teach them they have to be siblings and force them to get along, then you wont have a problem. You have to be the leader of the family (or your wife), and they will respect and follow your wishes. I knew getting a small dog after having the lab could cause a problem, but I separate when needed and make sure they get their own love and affection times.