Thanks for the additional information. I really appreciate it.
Actually what you're seeing is absolutely normal puppy behavior and you really don't need to break it up when they're wrestling or when Bella is being 'mean' to him.
Puppies need to do this wrestling with one another so they can learn about important things such as dog-on-dog interaction, bite inhibition (learning to soften their play bite when their sibling yelps), and other doggy body language such as figuring out pack hierarchy.
There's a great website that explains all stages of puppy play here:
I would suggest that you STOP breaking up the play fighting. By interrupting them when they're play fighting, you can actually cause problems with them as they age since they won't have gone through the necessary stages that it takes to be a dog who understands body language of other dogs and can actually lead to more significant fighting at a later stage.
It's also important to keep in mind that even though they're both puppies, they're VERY different breeds and therefore will act differently from one another. Bella is a terrier...known to be tenacious, bossy and fearless. Bembesito is a Havanese...which are known for being a lot more laid back and mellow. It's just in their nature to play and behave differently, so you can't really compare them.
But just to reiterate....this sounds like very, very normal puppy behavior.
Enjoy the puppies!!!