I just found another one that doesn't fit the pattern. Parents are #14 and #15, but the child is a #9. He's the only black haired child I have now.

I wonder if in these cases, only one half of the "outside" numbers are being used? For the first example, parents are #9 and #10 with the child being #18, if you only consider the larger part of the "other numbers" (numbers 11-30), the 18 might make better sense. 11 + 30 = 41. Half would be 20.5 so a #20 or #21 are equally in the middle. So an 18 is only 2 points away from that middle.

In my other example, with parents being #14 and #15, one set of numbers is 1-13. So 1 + 13 = 14, divided in half = 7. 9 is just 2 points away.

It's interesting to note that in both cases, the parents were only 1 point away from each other.

Two of these examples isn't enough to verify a pattern, but it's something to watch for. If this does turn out to be a pattern, then that'll be the key to getting black or blonde haired heads when you don't have any to start with.

My kids have to grow up so they can breed for me to try this out more. Some of my elderly adults are dying out so, hopefully, I'll have enough available characters to try this out when the kids turn 18.