Where did the red hair come from?

Here's a picture of my kids, both of whom are gingies:

Ella (left) and Jake

Since neither I nor Andi (Mum) is a red-head we are incessantly asked "Where did the red hair come from?"

Popular answers include:

• Postman Pat
• Alien abduction
  
• They are freaky mutants
  

Incidentally, none of their grand- or great-grand-parents were red-heads, but they have a few carrot-headed cousins.

Apparently the genetics of red-hair is not simple. In particular, it is not just a case of a recessive gene hiding away for a few generations.

Andi and I are not planning any further children. I have suggested that we try for a non-redhead, but the danger of a third gingy has proven to scary.