Hello Dunlata,
Your John McSephny, born 1857. you say you have got his birth certificate, did it say for sure what his mother Helen's, surname was ie Martin, or Morton, both names would sound quite alike its only a case if whoever registered the birth could not read or write then it may have sounded like a Aryshire, dialect to the register.
I think the parents were indeed John, and Helen Martin, this couple had at least three more children in Ayrshire,
Margarert Mcsephny, born 21/Aug, 1859. Colyton, Ayr,
James Mcsephny, born 16/May/1864, Dalrymple, Ayr,
Helen Mcseveny, born 30/April/1866, Kirkmichael, Ayr.
The marriage for John Mc*evny, and Helen Martin, comes in 1856. St. Quivox, Ayr.
If you get this marriage it should give both sets of parents for the couple.
I think John's, father was named John, also, and his mother Elizabeth.
The spelling of John's, surname has lots of twists, and is difficult to reproduce on the IGIs. soundex system.
If you get the marriage i should be able to confirm his parents, and maybe Helen Martin's, parents also.
Regards,
Jonn.