It can't hurt to have a backup.

You can't prevent a possible future closeness between your upcoming child and one or more of their grandparents.

If you get a dog, take care of your dog! You can just not have a dog if you don't feel like taking care of one, it's very easy to not have a dog.

It is so tempting to return rudeness with rudeness!

There are alternatives to pregnancy if you want another child.

You are allowed to draw lines even if your feelings are irrational. Part of the marvelous business of being an adult human is that you get to set your own boundaries for whatever reasons you like, without appending a sensible rationale to them.

It can't hurt to have a backup.