If you go to a Family History Centre and find out that Mary Ann's father was indeed Isaac Wilson, you should also order Cath's parents' wills, which are next to each other on LDS film no. 0106241 (Brian Lawson's index: KISSACK, Robert [year] 1818, [place] Lez, [Arch will] A [number] 56 [film no] 0106241). His wife Mary's will is no.57.
It appears that these are where Revd Kissack ["Seed of Isaac"] got his information about the marriage of their daur Cath to Isaac Wilson, and the names of all Cath's siblings, because I can't see their bapts on the IGI. Nor Robert's two marriages given by Revd K.
IOM wills are very informative, and often give details not found elsewhere.

The 1841 census, on which adult ages were rounded and no relationships given, have Isaac and family at Glenmoar, Lezayre. Isaac Wilson 65 b.England (I can't read his occupation - something joiner? - someone else might decipher it), with other Wilsons: Cathrn 60?, Cathrn 20, Elizth 16, Mary 15, all b.IOM.

Sue