Yes, he is illegitimate ("unehl.", which is abbreviation for "unehelich"), and his father is "supposed to be Johann from Übers Mohr". Note that there are a lot of moors or bogs in this area, so "Übers Mohr" may merely mean "other side of the moors".
Full translation: "Margreta Aberlings from Abheriche's illegitimate son Johann Henrich; the child's father is supposed to be Johann from Übers Mohr.
. . . . "