would appear to confirm my original suggestion near top of this message group - the illeg gson of Thomas Stevenson (ggfa?) isn't proving easy to find - can't immediately find an match in presentments - but being Thomas's wife's nephew as well ?? - I think the two wills are summarised on MNB - Thomas 1780
breashen ?[probably my attempt to decipher Botchin but done before I could take photos];made 15 may 1769;son john,thos, robt; (sledge + limestones);gson wm stevenson;wife alive;dau margaret cowley;his grandson s/o son thos that he had reared
and
Ellinor 1782 - dated 4 sep 1777;sis cath,margt skelly als moore exex

I think Thomas might well have come from Douglas as a Thomas Stevenson shopkeeper buys property in Marown earlier but havn't yet matched the deed of sale of Botchin - I can find the transfer to the Cubbon's but not onwards - more work in library end of this week.