Test Child
The first child in a mother and father's relationship. They are the ones that have the roughest time usually, and are used as a little test run to become a better parent overall. They're usually the child that the parents go hardest on, and in worse parents, it'll stay that way.
Person 1: "We should have children!
Person 2: "Yes, definitely!"
Person 3: "Don't, you have no experience, you'll create a test child."
Person 2: "Yes, definitely!"
Person 3: "Don't, you have no experience, you'll create a test child."