Jax, my 6 month old Golden is a tremendously gentle soul. He does, however, get very carried away when he plays with his new 3 month old sister, Lucy. He is only trying to play, but the size difference is scary. He is 48 lbs and she is 13 lbs. He mouths her softly alot of the time, but when he gets over excited, he gets too rough. He hasn't hurt her at all, but she has let out a yelp a few times. I separate them at this point for a few minutes until he settles down, but then hes at it again. Other times, they will lie in the same room together and play nicely. Does anyone have any suggestions??