This day in music history.

October 9, 1975, John Lennon celebrates his 35th birthday on the same day his son Sean is born. Sean Ono Lennon is John and Yokos only child together.
Birthday by The Beatles
You say it's your birthday
It's my birthday too
yeah
They say it's your birthday
We're gonna have a good time
I'm glad it's your birthday
Happy birthday to you.
Yes we're going to a party party
Yes we're going to a party party
Yes we're going to a party party.
I would like you to dance
Birthday
Take a cha-cha-cha-chance
Birthday
I would like you to dance
Birthday
Dance
You say it's your birthday
Well it's my birthday too
yeah
You say it's your birthday
We're gonna have a good time
I'm glad it's your birthday
Happy birthday to you.
DLAK note: John and Paul wrote the Birthday song years before Seans birth.