Just one

"Eric. That's the name of one of my husbands when I get older."
"Willa, what's my husband's name?"
"Uh.... daddy."
"And that's the only husband I have, right? Just one. How many husbands do you think you'll have?"
"One."
"Ever?"
"Yup."

Finally, our little polygamist is ready to agree to one and only. And - just to record for posterity - his name will be Eric, apparently.