This record was set in June 2002 when Denise Van Outen (b.1974) re-recorded the classic “Can’t Take My Eyes Off You” with American singer Andy Williams (1928-2012), who was 45 years, 1 month and 11 days older than her! The song had originally been released in 1968 by Frankie Valli, who took it to No.2 in the US, but was also recorded by Williams, who reached No.5 in the UK, that very same year. The Williams/Van Outen version made No.23.
For a same sex duo, we must mention Frank Sinatra’s (1915-1998) collaboration with Bono (b.1959) on “I’ve Got You Under My Skin” in 1993. Sinatra was 44 years, 4 months and 28 days older than the U2 singer.
And before you say it, Jessica Simpson’s (b.1980) cover of Nancy Sinatra’s “These Boots Are Made For Walkin'” in 2005, featured vocals from Willie Nelson (b.1933), who was 47 years, 2 months and 10 days older than Simpson. Nelson’s contribution to this song was uncredited (and also virtually inaudible), so this does not, officially, count as the biggest age gap!