Young at Heart is a soft-pedaled, musicalized remake of 1938's Four Daughters. Robert Keith takes over the Claude Rains role as paterfamilias to a family of musical prodigies, all girls: Doris Day, Dorothy Malone, Elizabeth Fraser (the fourth daughter was written out of proceedings, no great loss). Keith's new boarder Gig Young, a musical-comedy composer, becomes the three daughters' heart balm, whether he wants to our not. When he gets stuck creatively, Young invites his tempestuous pal Frank Sinatra to help him finish his score. Sinatra essays the old John Garfield role, retaining a generous supply of Garfield's chip-on-shoulder edginess. But whereas Garfield's character dies in Four Daughters, Sinatra survives for a happily-ever-after clinch with Doris Day. Most of the songs heard in Young at Heart were already standards in 1954--with the notable exception of the Johnny Richards-Carolyn Leigh title number, which of course became a part of Frank Sinatra's standard repertoire.
~ Hal Erickson, All Movie Guide