If I can join your conversation. My research has Isabella Marr's father as William born 1783, and mother Margaret White born 1787 in St Monans. The baptism records for St Johns Episcopal Church Pittenween show a Thomas Aitken born 22.12.1819 and baptised 09.03.1820, the father being Thomas and the mother Jean Allan - they were unmarried. He appears to be the only one who is the right age for the census returns later. I don't know if they were ever married or who this Thomas belongs to.