Imma guess the king is 'naturally' a scowler and he has no idea how to be un-brusque with anyone. That, and if the queen died from birth, he probably has mixed feelings about it, esp if the baby kept crying when she sees him everytime.
Or... he has a curse/prophecy that makes it so he has to kill her before she's an adult to stop something.
Will be interesting to see how it goes.