Harti and Khiri got Alk & Ilke in their teens
Look at the picture on Awesome
, they look tired, has bags under eyes, but that is because they're slaves. 16 year olds can get such thick beards, and Sha-ra tells Alk when he's 17 that he'll start shaving soon as sooner or later his beard will start growing. This can also explain why the mortoks didn't see Khiri's pregnancy.