Nuclear Family by Kate Davies

When Lena buys DNA testing kits for her father Tom and her twin sister Alison, she thinks they’ll enjoy finding out where their ancestors come from, and what percentage Neanderthal they are. She has no idea the gift will blow her family apart.
 
Tom is forced to admit that he isn’t his daughters’ biological father: he and his late wife, Sheila, used a sperm donor. He's terrified Lena and Alison will reject him, and desperate to win back their trust – whatever it takes.
 
Alison thinks DNA doesn’t matter. She and her wife are trying to start a family using donor sperm, too. To her, Tom is their dad, and that’s that.
 
But Lena becomes obsessed with tracking down their biological father. And when she discovers she has a half-brother – an actor with a blue tick on Instagram – she becomes obsessed with him, too…
 
From the author of the Polari Prize-winning In at the Deep End, this is a very funny and deeply moving novel about identity, donor conception and what it means to be a family.
 
-----
 
‘An exhilarating meditation on the meaning of family’ The Bookseller, BOOK OF THE MONTH