All the research I've looked through over my years of trying to trace my ancestral line, keeps coming back to a "John" du Plessis as her second marriage. The English version of Guillaume is William, and he would have used that name and if he did, his name would be recorded as Jean Guilliamme, but all the data on all the genealogy websites uses the latter rather than the actual husband, her second marriage. She died without issue. Therefore she cannot be the mother of a child born after her death
According to Wikipedia https://en.wikipedia.org/wiki/Margaret_de_Beaumont,_7th_Countess_of..., she died on 3 June 1253, her purported son, Pierre, was born in 1307 in Poitiers. Surely if he was he son, he would've inherited the title and estates through his mother, which of course the person Pierre du Plessis didn't. Can someone who is familiar with du Plessis history please correct this, or explain to me why my data is wrong when every reference to her stresses that she died childless and the estate was passed on to a cousin.
