That's novice stuff. It's a cheap emotional gut-punch that weakens that character's ties to the world and story. You can do so much more if you keep them alive:

• They can hand out quests, as they think their child could handle it.
• They can help out with certain tasks, like watching a tavern or storing stolen goods.
• They can be a good twist villain later in the game, because they're tied to the heroes.
• They can be a good fake-out villain, because it's suspicious you haven't killed them yet.
• Another PC can literally bang this PC's mum.