The youngest I know of was 2, but I wouldn't worry.  It is not genetic in most cases.  None of my kids have shown any signs of it, although I inherited insanity from them.

Jerry

I didn't get CH's until I was 32... and zero history of CH in my family.  Not even migraines, AFAIK.  Personally, I wouldn't worry too much about your kids getting them. From what I've read there doesn't seem to be any evidence of them being hereditary.   I have 4 kids... no real worries here.

Both my grandmother and my father experience headaches that resemble CH.  my grandmother attributes them to silicilate allergies.  Something I find odd is that she says about once a year or so she would eat something that she was allergic to around holloween and around Easter and that it would take one to two months to "get them out of her system".  I know they would put her on the ground screaming...  My father gets short headaches behind the eye that makes him stop in his tracks and go for a brisk walk for an hour.
I wonder where I learned not to seek treatment when I was younger

Migraines run in my family (grandmother, father, me, son and now grandson - age 10) but so far no CH that I can see (Son I've got doubts about, but think he's just having migraines).

There have been a few on here who've had their kids come up with CH, but very few. So far we haven't discovered any genetic link. IMO - don't worry about it unless the kids start showing signs - then you can worry.