Advice columnist Pauline Phillips was born on July 4, 1918, and so was advice columnist Eppie Lederer.
Movie couple Catherine Zeta-Jones and Michael Douglas were both born on September 25 (1969 and 1944, respectively). Same as me!
Rock musicians Pete Townshend and Joey Ramone were both born on May 19, the former in 1945 and the latter in 1951.
Football teammates Franco Harris and Lynn Swann were both born on March 7; Harris in 1950, Swann in 1952.
Tom Watson and Ray Floyd, PGATour golfers were born on September 4, (1949, 1942). They each won 3 different major championships in golf.
As you mentioned, and as I immediately forgot. Sorry.
Sorry also with same lame excuse to you Giles.
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I can assure you that Baxter and Gross are not identical twins and, in fact, have no genetic family ties.
John Lennon and Julian Lennon were both born on October 9th. So was Sean Lennon, but AFAIK, he’s not a musician.
Wikipedia says Julian’s birthday is April 8—? John and Sean were born on October 9, though.
. . . along with Alastair Sim, Tony Shalhoub, Scott Bakula, and Mr. S. 
According to this wiki article, given a group of 23 people, the odds are 50/50 that two of them will share the same birthday.
Fighters Chuck Liddell and Manny Pacquiao were both born on December 17, 1969 and 1978 respectively.
Ballplayers Jackie Robinson and Nolan Ryan, January 31 (1919 and 1947).
Nazi Party leaders Herman Goering and Alfred Rosenberg, both January 12, 1893.
He’s a multi-instrumentalist and singer who has released solo albums and has played as a sideman with different bands.
Speaking of twins, nobody has mentioned Maurice & Robin Gibb of Bee Gees fame (born December 22, 1949) or arguable the most famous set of acting twins in the world, Mary-Kate and Ashley Olsen (born June 13, 1986).
Another baseball one: Key Griffey Jr. and Stan Musial (Nov 9), in the same town too oddly enough, albeit 49 years apart.