It is more than a possibility it is a valid and optimal tactic.
If a noble dies without a valid heir i.e. You killed his children and he doesn't have any hidden away elsewhere their title is left in a power vacuum which leads to those with a claim fighting over the title itself.
There was even a discussion about removing the NPCs of a kingdom to rob the players of the manpower they would provide.
Now that said it has been mentioned in a QA or two that SBS is aware of the angst some folks have about losing their family and are looking at adding a revival mechanic for certain important NPCs. Whether that means those of certain status or those who are family your guess is as good as mine.