"She's your mom." "They're your family." "Blood is thicker than water." For generations, these familiar idioms have illustrated what Rin Reczek and Emma Bosley-Smith, co-authors of the 2022 book "Families We Keep: LGBTQ People and Their Enduring Bonds with Parents" (NYU Press), term compulsory kinship: the social expectation that biological and legal family ties must be preserved at all costs. In Reczek's new book, "Families We Lose: A New Explanation for Family Estrangement," published this week by NYU Press, Reczek explores what happens when adult children decide that family obligation is no longer reason enough to stay.