Mary Mcmillan and Alexander Mckirdy

Mary McMILLAN (or McMULLEN) was the wife of Alexander, mother of Alexander McKIRDY (b1807) I keep coming up against a Mary Wilson who Married an Alexander McKirdy and had a son, also Alexander. I found them in a census in Largs, Ayrshire, Scotland. I've been wondering if they're the same Mary who has perhaps been married twice. Would love to hear from anyone who had them in their tree.