Hello Lyn,
There is only one marriage for a George Clark, to a Rosina, in Ayrshire. this one was in 1917. in Galston, Ayr.
There is also a birth in 1927. in Galston, Ayr, for a George Clark.
There are no marriages in the period 1900. up to 1930, between a George Clark, and a Maria. in Scotland.
So there is a good chance that the George Clark, and Rosina, 1917. is your couple, and that the birth of George Clark, 1927, in the same place is also George, and Rosina's, son.
The only way to prove this connection is to take a chance and purchase the birth certificate for George Clark, born 1927, in Galston, Ayr. which would provide his parents names, and the marriage date of parents.
You can purchase this certificate for a small fee on Scotlandspeople.
Regards,
Jonn.