Shirley,

There may have been two Jane (or Janet) Houstons. There was certainly a Jane Houston, daughter of William Houston and Agnes Stewart as a "Jane" is listed in the 1684 list of the Episcopal curates of Galloway as a daughter of William Houston and Agnes Stewart. I agree with you however in that it is unlikely that this Jane was the wife of John M'Candlish since a daughter, Agnes M'Candlish was born to John and Jane M'Candlish before 1657. It appears more likely that as you suggest that Jane Houston, wife of John M'Candlish was the sister of the William Houston who married Agnes Stewart.

Thanks for the heads up. I'll make a change in my database.