Born to Lillian Jacobs, famous Witch fashion designer, and Carter Venesteela, an employee in the Accidental Magic Reversal Department, Marianne is a pure-blood through and through. Lillian was born in France, and came from French nobility. She graduated from Beauxbatons Academy of Magic, and went on to become a designer for Witches, and to a lesser degree, muggles. Carter was born and raised in Brighton to a rather rich family, who all worked for the Ministry to some extent. They're old money, and Carter went to Hogwarts, where he graduated top of his class, and a proud Hufflepuff.

They met after one of Lillian's fashion shows went awry, one of the invite lists got mixed up, and a few Muggle reporters had been invited to a magically enhanced show. They saw things they weren't supposed to, and Carter was part of the clean up crew. The two exchanged words, and found they immediately clicked. Having dated for quite a few years, Lillian got pregnant, and they decided to marry. Settling down in one of the Venesteela family that had been vacated for their growing family, Marianne was born a happy and healthy baby girl. Unfortunately, due to some complications during her birth, Lillian was unable to have any more children. This didn't deter them from being caring, and loving parents. 

While Carter had to travel quite a bit for work, Lillian made more of an effort to stay at their home in England, wanting to cherish her time with Marianne. When her mother did have to travel, Marianne was fortunate enough to go with her, and in doing so she saw many parts of the world. She became quite the mommy's girl over time, something neither of her parents had a problem with. 

When time came for her to start early schooling, her parents and their family decided it was best to invest in mostly private tutoring, in order to keep her from encountering any possible incidents of accidental magic usage. In doing so, they were able to let her freely explore her magic, being able to help and guide her through the sometimes scary process. While it was good for her learning, her socialization skills became lacking over time, not really being able to interact with children her own age. In an effort to get her more friendly, Lillian began to use the young Marianne as a muse for some of her designs, getting her small amounts of child modelling. While it did help a little, it mostly made her superficial, unable to properly relate to other children, due to the cold, professional setting. 

When time came for Marianne to enter into proper schooling for her magical abilities, her parents were stumped on where to send her. While Lillian had a strong preference for Beauxbatons, they both eventually agreed that Hogwarts would be best for her, in order to get a proper communal experience.