Hi there,
I have Baptismal records of children to Robert Fulton and Isabell Montgomery. The name Robert is quite numerous in the Fulton family tree. Both Isabell's first husband Arthur Lang and Robert Fulton were subscribers to the same religious publications (Phronema to Pneumatos or the Grace and Duty of being spiritually-minded, Declared and practically improved, and Epistologia: or, a Declaration of the Glorious Mystery of the Person of Christ, God and Man.) which indicates some form of familiarity. Isabell's marriage to Arthur Lang was recorded as the following: "31 Oct 1767, Arthour Lang, weaver and Isabell Montgomerie in Bank-End, daughter of Hew of Meikle-Cloak". Arthur died two years later in 1769. Isabell married some time between that and 1772 when her first child to Robert Fulton was born. Robert was also a widower at the time. The dates fit.