Hoping someone can help us solve this puzzle: Who are the 2 KEEFOVER (sp?) individuals below and how are they connected to the MALLISEE (many sp) family?

1. KEEFAVOR Adams County: Found in Allegheny Cemetery Pittsburgh, PA one Katharine KEEFAVOR in lot of Henry MALLISEE (MALLACY) died or interred 19 Dec 1858 marked 'grandmother'. Grandmother of whom??? [Katharine could be the mother of Sarah (nee ?)MALLASEE wife of Thomas who emigrated from Adams County to Pittsburgh in 1825 with son Henry b 1823 and possibly son William b 1822. The MALLASEE family was also in York & Fayette Counties] Henry's wife was Deliah DIEHL.

2. 1880 census - PA, Allegheny Co, Springhill Twp:
David KEEFAVOR, 62 yrs old, is living with the family of Henry & Deliah MALLASEE. He is listed as uncle - but, how??? Is David the son of Katharine?

Any leads would be greatly appreciated.