History
Cathy use to date Monsieur Jean when they were young adults. It ended to a break-up.
When she visited Jacques and Vero, she met Monsieur Jean again. They started to date again. This time it became a more stable relationship.
At one point, their relationship was at a difficult state, which is probably one of the reasons why she took a two-month job assignment from New York. Jean stayed in France. After some time (weeks, maybe) Jean goed to America, because he wanted to spend more time with Cathy.
Between the fourth and fifth Monsieur Jean-album, she gave birth to her and Jeans daughter, Julie. The birth happened off-panel.
Their whole family moved to another apartment in Monsieur Jean 6. After that, their life has remained stable.
Creation
Cathy was created by Philippe Dupuy and Charles Berberian.