I thought, "What?"
Of course, if I don't repeat what he says to show that I understand, Cooper will repeat the same phrase over and over and over again.
"Lincolns luff mee." (Seeing it spelled out, I wonder why I didn't understand it.)
"No, Lincolns luff mee."
After trying a few phrases, I finally I got it: "Lincoln loves you?"
"Yes! Lincolns luff mee!"
"Yes, Lincoln does love you Cooper. He's very lucky to have a brother like you."
What a sweet kid.