The little one is Bebe, a minpin, she's 9 yo. The big guy is our mastiff puppy, 18 months old at the time of the picture. He's 3 yo now, will be full grown at 4.
Yes, she runs rings around him. They are very close friends.
We have always had rescue dogs, until these two. Even Bebe was a gift from a friend who used to breed minpins. We had her neutered (she was too young to breed, and we didn't want to anyway) and Tinker, the big guy, is too.
When we got him, she mothered him and he loved it, in spite of him being 25 lbs and her 5 lbs. He followed her around everywhere, and she showed him the ropes. Even the first day, she showed him where to "go" outside, and he never had an accident, from 7 weeks old onward. Bebe isn't as smart as Tinker, but she's bossier. ;-D
They play, but he has never even nipped or scratched her.
Mastiffs are good dogs... I've had several breeds based on them ( bulldog and boxers ) and they make fine companions.