Jean Dumontet, dit Lagrandeur, was the son of Jean Dumontet of La Prairie and Georgette Foran. He was born about 1659. He married, at La Prairie, Elisabeth Casse on 6 November 1712. Jean Dumontet was buried on 22 May 1729 at La Prairie.
Elisabeth Casse was born Elizabeth Corse, daughter of James Corse and Elizabeth Catlin, in Deerfield, Mass., on 6 February 1696. She was captured in the Indian and French raid of 29 February 1704 and carried away captive to Canada. She was baptized a Catholic on 14 July 1705. In the next year, aged ten, she asked to become a citizen. In 1712 she had an illegitimate daughter by an unknown father. This daughter died very young. It was later that year that she was married for the first time. After a marriage of almost seventeen years her first husband died.
Elisabeth must have been an attractive widow, for in less than a year she married a man younger than herself. She married secondly Pierre Monet, the older brother of one of her sons-in-law. This marriage took place at La Prairie on 16 January 1730. After an eventful life she passed away at the age of 70 and was buried on 30 January 1766 at La Prairie. This Pierre Monet had been baptized 19 March 1704. He was buried at La Prairie on 16 February 1774.
Elizabeth Casse's second husband was the elder brother of her son-in-law (that is, the husband of her daughter by her first husband), and Elizabeth Casse had children by both her husbands (see the diagram below). So Elisabeth Dumontet's brother-in-law was her step-father, and she was an aunt by marriage to her half-siblings. And the children of Pierre Monet were related to the children of François Monet not only as first cousins, but also as half-uncles and half-aunts. (Genetically, the two sets of children shared 1/4 of their genes, the same degree of relationship as between a grandparent and grandchild, as between half-siblings, or as between a full uncle/aunt and niece/nephew.)
In other words, Elisabeth Dumontet was her own step-aunt! (That's not quite as impressive an accomplishment as being your own grandpa, but still plenty confusing.)
1699 François Monet ==== Marie Dumas 1661-1746 | 1675-1753 | +------------------+--------------------------------+ | | | | | 1712 1730 | | Jean Dumontet ==== Elizabeth Casse ==== Pierre Monet | 1659-1729 | 1696-1766 | 1704-1774 | | | | | | | 1732 | children François Monet ==== Elisabeth Dumontet 1706-1762 | 1717-1767 | | many children