There is a marriage for William Nelson to Elizabeth Keenan at Cambuslang in 1935. Alongside it, there is William McHardy married to Elizabeth Keenan, 1935, Cambuslang. Both these entries have the same GRO number so these two marriages actually refer to the same people.
So they married in 1935.
There was a William Thomas Nelson born 1936 at Cambuslang, Lanarkshire and a Thomas Gerald Nelson born in 1937 at Cambuslang, Lanarkshire, so this appears to be the two sons you mentioned. ...There is a Thomas Gerard Nelson, who died aged 72 in 2010 and this death was registered at Martha street, in Glasgow.
I know Gerard is different from Gerald. However, Thomas Gerard Nelson was aged 72 when he died, which would make his birth 1938, and as Thomas Gerald Nelson was born in 1937, there is a possibility that this just might be him.