The Subtle Power of Indiscretion by Alexander McCall Smith
This is part of the Isabelle/Jamie series set in Edinburgh. Isabelle runs into an old school acquaintance while having coffee one day. The woman, Andrea, tells her that she discovered that she has a half sibling she never knew about--who wants to meet the rest of the family. She is trying to protect her elderly mother and wants Isabelle to convince the brother not to contact the rest of the family. Then there's a plot about a concert promoter who has eyes for Jamie--unbeknownst to him but quite clear to Isabelle. And 2 of Isabelle's professional acquaintances, Professors Lettuce and Dove, pop back up and drag Isabelle into their power games. All in all, it's kind of a typical week in the life of a philosopher and her musician husband.