Are you home, or at University?
At home. You can't have children at University. Not even cloned ones!
Update: I stalked the Langerak kids home from school and neither one of them can be tutored either.
Update 2: I had another Sim in the household get to level 5 logic. They were able to tutor without an issue and without the family-oriented trait. I think it's because my other Sim learned her logic skill while at University. I went back to an earlier save of the game right before she had graduated. I didn't have her learn the last skill point in logic before she traveled back. Cloned another kid - still couldn't tutor. I stalked the Langeraks again - still couldn't tutor. However, when I had her learn the last skill point, she gained the ability to tutor.
Moral of the story: Don't have your Sims max out logic and possibly other skills while at Uni.