How did you determine who will get custody of your kids if something were to happen to you and your SO?

I personally feel like parenting style means more to me than a close family connection. I'm an only child and my husband's only sibling has the brattiest kids in all the land due to lax and technology heavy parenting styles. My mom is poor but she would step up and be a more strict guardian than my rich in-laws and that is what I want for my daughter because that is how I intend to raise her.

What did you look for when deciding who would care for your children if disaster struck?