Alright, how's this, then:<br/><br/>Begin with a Mirror Mephit.  CR 3, 4 HD.<br/><br/>Apply the Half-Nymph template, which adds on a number of lovely items, including an entry titled 'Awesome Beauty'.  +2 CR, bringing it up to 5.<br/><br/>Next comes the Half-Minotaur template.  CR +1, increases size up to medium and adds on a nice pair of horns.  Then Half-Vampire, CR +2, picking the Charm Gaze ability for his one special power.  After that, of course, is CR +0 Amphibious, since he'll be taking after his father in the aquatic aspects, as well.<br/><br/>The next template added is Mirage Mullah from Sandstorm.  CR +2, changes him to a Fey, grants Daylight Weakness, a number of nice Spell-Like Abilities, and he also gets the 'Oasis-Dependent' weakness, which should probably be tied to his father's divine realm, rather than a desert oasis.  It should be able to be gotten around with the right item, as well...<br/><br/>The final template, to get him back to the Outsider type, is the CR +3 Unholy Scion.  Total CR at this point is 13.<br/><br/>Then come 12 Outsider HD, bringing him up to CR 19, and the remaining 8 CR are filled in with class levels, 4 in Paladin of Tyranny and 4 in Hexblade.  Hexblade switches out the familiar at 4th for the Dark Companion ACF, while his two epic-level feats will be Widen Aura of Despair and Improved Aura of Despair, making him into a nice, army-level save debuffer. ^^<br/><br/>End result is Charisma 42, after the +2 stat increase, +4 tome, and +6 item bonus, and he'll have some nice illusory and charm abilities, plus that 1/day Simulacrum to provide him some nice meatshields.  Overall, I think he's a son you'll be happy to have follow in your character's footsteps. ;)