I'm a bit confused here;
So who was this Frances?
Marriage FreeBMD 1858 Frances PETCH/George CROSS on same page.
FreeREG has the Marriage;
05 May 1858 St Margaret, Laceby
George CROSS, Full Age, Bachelor, Labourer, Father EDWARD a Labourer
Lacfrances PETCH, Full Age, Spinster, Father WILLIAM Petch a Gardener**
Witnesses, William Petch/Eliza Cross
1851 as you say Frances is Fanny Petch, living with her Parents.
1861/1871/1881 Frances CROSS is born c 1831 Laceby
1891 the Family appears to be in Canada
Trish
