The parents of Mencke Jans are a bit more difficult to predict, but his father might well be: Jan Harms, who at his marriage to Grietje Jans (22-01-1682) was "wonende op de Knol te Rottum" as this would explain the surname Knol. (de Knol is apparently a farm between Stitswerd and Rottum.) Menke should be a son by an earlier marriage. Two possibilities exist:
Jan Harmens and Geertjen Geertz (7-11-1669) Jan Harmens (Schipper) and Krijnie Hindrickx (27-11-1670)