www.scotlandspeople.gov.uk is the only site for this info. It is pay per view via purchase of credits
Download a copy of his 1942 marriage cert which will give his parents names and mothers maiden name
If he died in Scotland & you know his actual year of death the entry on SP may possibly show his mothers maiden name - but not all entries show this info
If he died in 2003 in Lanarkshire - his mmn was McGeoch
In which case these are his parents
WILLIAM SWAN/ MARY MCGEOCH
1911 648 / 64 Lanark