There is a summary of Joney Killip's will on Manxnotebook (she was my suggested mother of Wm based on age at burial) however the will does not mention a Wm and the gap between Wm to next child suggests that wm died in early childhood - thus I can't see any obvious parent in Arbory but Wm might well have been born in adjacent Rushen - he might well be illegitimate but I can't see any match here either