Tangled Lives by Hilary Boyd
Lizzie Delancey is happily married, in her early 50s, with three grown children. But Lizzie guards a dark secret. At age 18 she had a baby boy, and gave him up for adoption. She still thinks of him every day. Then, out of the blue, she receives an official-looking letter from Kent Social Services. Her son, Daniel, wants to make contact. On one hand she is overjoyed - she longs to meet him. On the other, she has never told her children that they have another sibling. Tangled Lives follows the effect this revelation has on her family, as, with Daniel as the catalyst, a few small tears in the family fabric suddenly gape wide.