Hi Caroline,
My gg-grandmother was Bridget Jordan @1840 iish. She married Edward Byrne and they had 8 children that I am aware of ...Elizabeth, Ann, Mary, Catherine, Bridget, Johanna, John, and Michael. A few of them moved to Chicago, Illinois. Couldn't locate their marriage certificate. Perhaps, iif your mum has time and at her convenience, she could ask.
Thank you
Barb