Title of the Book??

Question

I'm trying to recall what this series is...
Basically it was about a girl and her sister who found themselves living underground with Goblins or something. THe goblins were "ugly", at first, to them, but eventually the girl married the Goblin King and they had a son, and adopted a strange human girl?

Can someone help me? I loved the first two books of this series...I'd love to find and read them again, as well as the ones that MUST have been released by now...

Thanks!

Answer 1

labyinth