Actually, it was his grandson. Also, it wasn't so much a killing as a sacrifice. Furthermore, Steven was chosen because he was convenient - there were no other children in the vicinity - and also as a form of expiation for the "original sin" of turning the first twelve children over to the aliens forty-four years earlier (Captain Jack had been involved then also).
The more you think about it, the more you find that the entire plot is rife with allegory and symbolism.
Good point about expiation for the original deal, and the plot being rife with allegory and symbolism.
I don’t like Russell Davies but he’s certainly a good writer.
I’m looking forward to Doctor Who’s dust planet tonight!
See ya’,
Ed