There's no reason why Maggie couldn't have given birth to Phleg and Brewmaster. Phleg may look a lot different, but I'd have just thought that was because he's brutish character, and developed that way. Brewmaster's green complexion is probably down to the time he spends with Brew.
But your theory about 'Princesses' makes sense, and I think it's been applied to Mudokons before. About them, I came up with the idea that these Mud Queens-to-be are kept locked away in towers... so Abe can come along and rescue them.
But pertaining to such Glukkon females, I'm not sure what their role would be. I can't imagine Maggie would let them have a sector of the Cartel to themselves, although that would introduce some interesting concepts. Equally, I don't think they'd be branded as Albino Slig larvae and exterminated. Ideas?