Which child of Rebecca and Alexander are you descended from ?
My GG Edward BOAKE 1807-1897 was a brother to your Rebecca BOAKE 1803-1890!! Edward married his cousin Sarah BOAKE 1818-1881. Other siblings of Rebecca and Edward were: Elizabeth BOAKE 1792-1871 who married Bartholomew BULL, and John BOAKE 1804-1895 who married Rebecca BOAKE 1805-1867 (a first cousin, and half-sister of his brother's wife Sarah).
The parents of Elizabeth, Rebecca, John, and Edward BOAKE were possibly Edward Boake and Eleanor BETHELL who married in 1791 at Borriskane, County Tipperary, Ireland.
The parents Sarah and Rebecca Boake and siblings Anne, Jane, and Maria, may have been Benjamin BOAKE and Sarah NORMAN.
It's confusing, to say the least, but info is from a privately published book "The Boake Family in Canada 1824-1874" by Ersyll and Ivadell Boake, of which I have a copy. Let me know if you need more info.