Jennie Trewhella was the wife of Mathew Trewhella III, mother of Sapphire and Conor, and the girlfriend[later wife] of Roger.

Jennie was deeply saddened at the 'loss' of her husband, Mathew Trewhella III, in the beginning of book one, Ingo. Jennie, truly believing that mathew is dead, starts to move on and eventually begins to date an Australian diver, Roger Grayson.

During the series, Jennie becomes suspicious of Conor and Sapphire's whereabouts, leading Sapphire to think she might know something of Ingo. Ultimately, she never learns of her children's presence in Ingo, or that Mathew had not drowned in the ocean. She and Sapphire argue about keeping a dog(Sadie) in books one and two before Roger steps in and convinces her, earning major brownie points.