Do wizards bred true in your setting?

[Shostak]

In my Myriangia game world, anyone with sufficient training can cast spells.

But I have another game world (on hiatus) in which the potential for wizardry is inborn. The trait goes to seventh sons of seventh sons and third daughters of third daughters. If there is an unbroken line for seven generations for men or three generation for women, that child will make an especially powerful wizard.