Looking at this ep recently after downloading TCW off iTunes (never watched it before) I think at least one of the kids is definitely biological.
One of them has full length head-tails and the Twi'lek cone ears.
The other has shorter, stubby head tails, and more human-like ears.
I must say I was taken by surprise. Interspecies breeding and successful production of offspring is common in ST of course, but I had thought SW deliberately steered clear of it... I guess I thought maybe GL thought it was silly...
Evidently, not so.