No birth of a Thomas predating the marriage. But starting around 1700 and earlier the records become quite thin.
Marriage of Thomas Sabiston & Anna Gorie, 1732-11-16, Kirkwall & St Ola [IGI/OPR Index: 1732-021]
And the baptisms of their children:
John Sibiston (M), 1734-05-25, Holm [IGI/OPR Index: 1734-019]
David Sibiston (M), 1736-01-25, Holm [IGI/OPR Index: 1736-019]
Jannet Sibistoun (F), 1738-01-24, Holm [IGI/OPR Index: 1738-019]
Magnus Sabiston (M), 1740-10-19, Kirkwall & St Ola [IGI/OPR Index: 1740-021]
Ann Sabiston (F), 1743-04-24, Kirkwall & St Ola [IGI/OPR Index: 1743-021]
There is nothing on Ann/Anna predating her marriage either.
Don