THey are both babies! And their play is how they work out their hierarchy.
I have this situation at home, too. My 10 month GSD, who was a "little puppy" when we got her (8 wks) compared to our 1 year old English Bulldog, has decided early on that she is in charge. She loves Rugby, but she collects/hides/takes away his toys (we give them back), and over the last few months, this behavior has decreased as she has matured. She still is alpha, but no longer feels to need to assert herself, since he recognizes her as such.
And they love each other - very concerned if something is wrong with the other one, they give each other kisses, etc. They can play very sweet and roll around wrestling in slow motion, and they can also really play rough. But they have learned bite inhibition and do fine.
So, what did I do? I alternated treating them as alpha (giving treats first, playing first, feeding first), with treating Rugby first most of the time - just not all the time. I would take away Rugby's toys from Myah, and give her back her own. I felt like this stage would never end. They both got one on one time with me and together time with me. I was very clear with my expectations and Myah tends to be very sweet, so she got the picture.
However, she draws the line in my bedroom. Rugby isn't allowed in (according to her), so we are working on that. I pick him up and bring him in, plop him down at my feet and work on my computer while Myah begrudgingly deals with it. lol.
So, yes, you are picking up on a hierarchy being established. Others will probably have better ideas than me. But this is what's happening in our house with two young dogs. LOL!