Hello Linda,
The parents names of William John Mcginn, born 1864 Stevenston, Ayr. were John McGinn, and Maryanne McCurry. but be aware of the spelling of the name McCurry.
On the 1861. census index for Stevenston, Ayr, there is this family.
McGinn MaryAnne, age 40 years, born Ireland,
McGinn Patrick, age 6 years, born Stevenston,
McGinn Hugh, age 1 year, born Stevenston.
There is a birth for Hugh McGinn, in Stevenston, 1860, to parents John McGinn, and MaryAnne McCurrie.
The father John McGinn, alas is not with the family in 1861.
Regards,
Jonn.