Originally Posted by cbn42

I don't think any airline is going to allow a small child to sit separately from his/her parent. If the child is young enough, the airline will do whatever it takes to make sure that at least one parent is sitting in the next seat. There is simply too much risk of things like sexual harassment of children, and they don't want the liability. Remember that the airline has the authority to assign you to a different seat for any reason.

So take your pick. Either move when the parent asks you, or wait for the FA to come and force you.