Magnus is 15.5 lbs and Zoey's 5.5 lbs. I haven't had any problems. And if I were to point out to a bully, it'd be Zoey. Magnus lets her get away with almost anything. But he will let her know who the real boss is between the two if she oversteps her boundaries.
IMHO, I think it'd be better to look at the personality of the dog than size. If both are submissive, no problem! But if Lexi's more on the dominant side, it'd be easier for them to get along if the new pup was submissive. |