This is the final track on The White Album, which was a double album released in the UK in November 1968. It’s a tender ballad written by John Lennon and sung by Ringo Starr, whose voice suited the song’s mood perfectly. It was completed with a lush score by Beatles producer George Martin, who also conducted the orchestra of 26 musicians. Along with the Mike Sammes Singers choral overdubs it was all consigned to the oxide particles in a late night session in Studio 1 at Abbey Road on July 22, 1968.
Many have thought this was a Paul McCartney song due to its gentle nature, but it does show John could write for the two opposite ends of the spectrum from the rockers like “Revolution” to the gentle “Julia.” (thanks, David – Wolverhampton, United Kingdom, for above 2)
John Lennon wrote this lullaby for his son, Julian. Julian did not discover this was written for him until 12 years after it’s release on The White Album.
Ringo sang this accompanied by a 30 piece orchestra and a choir. He is the only Beatle to appear on the song.
The Orchestra was scored by Beatles producer George Martin.
Songfacts from http://www.songfacts.com/detail.php?id=175
Smart People I Know 
I sang this song, as a lullaby, to both of my children every night. Even now, some 15-20 years later, they STILL love it!
(I suspect that THEY will inevitably sing it to THEIR children, one day too!)
Thanks for the background info on this beautiful melody!