Actually no, it depends on WHEN he decided to do away with his wife. For instance -- and this seems to me to be true based on the rapidity with which he ordered the cyanide from his own lab and then within 2 days his wife was poisoned -- that he had NOT decided on killing his wife until very recently, perhaps even within a few days to a week of the actual poisoning episode. So it could very well be that he and his wife BOTH had wanted a child the past year or so, and that it was not until very recently that he either discovered his wife might have been cheating on him, or he finally decided to do away with her because of her lies or that she disobeyed him or whatever he deemed he could no longer accept. In other words, they could have both wanted a child together very badly until recently when things came to a head between them, when his controlling manners and suspicions of her out-of-town trips became too much for him to bear and he decided enough was enough and she had to go. So again, no, the assumption you've made that because he killed her it absolutely meant he never wanted a second biological child with her may in fact be false.