I wouldn't change. You both know that you came up with the names separately and didn't 'steal' them as such.
I had DS's name picked out long before he was conceived. Then when i met my doula, she had a son who had the same first name. We are now really great friends and see each other frequently. The boys are both born in April (one the 20th and one the 22nd) just a year apart and neither of us mind. We just have a Big William and a Little William when we are together