Col has given you birth of Geoffrey/Jeffrey. The Manx BMD index for marriages has been down since March for updating, so cant check for Marriage. Brian Lawsons Marriage index only goes to 1923. No marriage on UK BMD.
Very hard to track people in this later period.
The following births registered in Castletown are possible siblings;
1937 Anthony Eden Buried 1972
1940 Juan Athol
All of the above initials are on Manx Telecom White pages excepting Anthony and Wendy, Wendy of course may have married.