You may already have your answer, but the Paulus book (pg. 148) lists a John
Umstat, born about 1740 to Gertrude and Henry Umstat; married his cousin
Isabella Boors (she is daughter of Margaret and Goshert Bohrs; also listed as
Sybella Bohrs; born about 1747; died before 1793). He died October, 1819. His
siblings were Harman, Henry, Ann and Mary.
Hope this helps.