Board Thread:General Discussion/@comment-25028999-20140801192152/@comment-25608247-20141101084148

I have a theory where it is possible for gems to reproduce with other species, but the resulting offspring wouldn't be gems themselves. My basis for this is the idea that a gem's true body is literally their gem; the human-like forms we see are merely convenient extensions created by the jewels. Given their versatile transformation abilities, I don't think it would be a stretch for them to replicate human reproductive organs in these bodies as well.

The reason Rose gave up her gem to create Steven might be a more personal manner. Just because a gem can have children doesn't mean that its necessarily a good idea. She would know fully well that, as a gem, she would live on agelessly for centuries if not millennia while Greg and a human Steven would die in a matter of decades. Not wanting to bear this pain, she chose to pass on her gem to Steven and disappear instead.

Probably a shot in the dark, but that's my idea.