We do not know our loved

Book subtle, endearing characters.
During Christmas Eve, a man announces to his wife that he leaves her for a man, after 11 years of living together and two children: it is "the exception". Icelandic is added to cold cold break
But in all this cold radiates heat of the characters: the heroine, his children, the next big heart, ornithologist lovers etc ..
This book raises the key question: we know the people we love the heroine asks:? How did such not included in the 11 years that her husband loved men she knew how the double life of her mother why did she met her biological father just before he died?