Half Sister, The by Sandie Jones; 2020. Softcover.

Kate and Lauren meet for Sunday lunch every week without fail, especially after the loss of their father--but a knock at the door is about to change everything. A young woman by the name of Jess holds a note with the results of a DNA test, claiming to be their half sister. As the fallout starts, it's clear that they are all hiding secrets, and perhaps this family isn't as perfect as it appears.