Puppy sibling rivalry

[Twodogs]

My two 7 mo. old lab puppies seem to get along great (male/female-brother/sister) until they go outside. I cannot walk them together (for one they are too big and aren't completely trained not to jump or pull when they see other dogs) because the male attacks the female. They appear to be playing so it is more of a bullying. He growls and she rolls over and continues to fight. There is never any blood or they never seem to be really THAT mad but I don't want it to escalate and I hate seeing the male bully the female (she's about 15 lbs. lighter but with a lot of fight). Could they really be trying to see who's alpha? She seems submissive to all other dogs and even to her brother but still has a big smile on her face and acts like she likes it. I know it's no good for them to continue this. Any thoughts?

[Lyka_01]

Sometimes I encounter problem regarding rivalry to my dogs Mha-ih and Sangro...they fight usually when eating time I don't know but they have separate plate...But after that they are back to normal like nothing happened...