DS had thin hair. After DH cut it 2-3 times (grade 4 cuts, which was too short) it's now super-thick, just like mine. And it's the same colour mine was as a child, so maybe it would have happened anyway.

But before you could see the cradle cap through the hair, now you can only see the cradle cap when you search through the hair, even with a grade 8 cut. (At age 3, is it still cradle cap? DH did remove it all when he was 1, but it came back.)