Mary was illegitimate- her birth registered by mother Sara Pollock but since father's details included he must have gone with her to register the birth.
Does Mary's marriage give her as single? (wondering if she m.1 Walton)
David King, son of Thomas, who is the man I suspect was Mary's father died in Greenock in 1915 and was living there at least by 1901.
Will do a bit more digging on Pollocks and post more details if and when I find them.