... I think it very possible that all of Charity's kids inherited talent from their mom, but nothing out of the ordinary, or like their mom they chose not to pursue it...
Word of Jim says otherwise.
None of the younger kids have
any power,
specifically because Charity was abstaining from magic use.
Now, this still follows "natural" law, the "rule of science:" epigenetics is the study of how genes express, of how environmental/dietary/etc factors alter the
expression of genes. It'd be unsurprising if active magic were an epigenetic factor (raising the question of whether just "hanging out with" a very-actively practicing wizard, or having lots of spells cast upon you, could activate latent genes).
But it also doesn't rule out
supernatural law(s) that might override "natural law" in some magical way(s).
We don't have any canonical or WoJ info on this, AFAIK.