hya well dunno if this is any use but i had 2 rabbits once brother and sister,(but i thought they were brother and brother) and they were in the same hutch and one day i noticed the black/white bunny getting fat (thought i was overfeeding) and the albino being very protective of me touching the other one-
then came the ickkle bunnies
agggghhhhhh
i thought they were brothers
i know its probly different to our little puppy pals but they didnt seem retarded and they had all of the correct body parts!
i know it might not answer ur question but just thought id share my story!
its probly not recommended as they cud have lots of problems mentally and physically!
love vikki and rambo