Nairb was 30 when he met Felissiara. She became Nairb's bodyguard sent by the Scarlet Crusade. She became his mistress. Some speculate Jonthus is their child. Nothing has been proven. All we know for sure is that he is in his teens and is Narb's personal slave and assassin. We also know Nairb got ahold of him in an "orphanage" in Stormwind. Since he never knew his parents, he decided the shadows would look after him. Jonthus was raised by Nairb's assassins and Kalora who felt sorry for him.