In 1967, the pair became the only father-daughter duo to top the Hot 100 with what DJs dubbed 'the incest song.'

"HEADED RIGHT FOR THE NO. 1 spot on the Hot 100," read Billboard's review of Nancy and Frank Sinatra's "Somethin' Stupid" in 1967, and the prediction soon proved true.

On April 15, 1967, five weeks after the review was published, the song topped the chart, where it reigned for four consecutive weeks.

The single, the only father-daughter duet to hit No. 1. Frank was then 51, and Nancy, 26, would rank at No. 7 on the year-end Hot 100 recap and scored dad his sixth Grammy Award nomination for record of the year.

The song also generated controversy because it's sung from the point of view of two lovers. In 1996, Nancy told NPR's Fresh Air that DJs dubbed it "'the incest song...' It gave them something fun to kid about."

Frank and Nancy would pair up again for "Feelin' Kinda Sunday" in 1970 and "Life's a Trippy Thing" in 1971, but neither tune charted on the Hot 100.

Meanwhile, "Somethin' Stupid" has endured. A cover by Robbie Williams and Nicole Kidman was a hit in the United Kingdom in 2001. In 2012, Michael Buble and Reese Witherspoon covered it on Buble's No. 1 Billboard 200 album, To Be Loved.