Tell him his parents could've done way better.

Let's hope the kid meant that your boyfriend could do better at working at the daycare than you

Just tell him he's adopted, auto win.

I'm sure the kid was just kidding.

Adoption is the win

And OP shouldn't let an opinion of a child under 5 years old, rule their life.

OP shouldn't let the opinion of anyone rule their life.

Keep their mouths shut

That is very true. My mom is a school bus driver and I cant believe some of the crap that comes out of the little 3rd graders mouths. They have no filter and just say what they want.

People can be arseholes, age doesn't come into it.

Disney, sadly.