The Most Fun We Ever Had by Claire Lombardo

MEET THE SORENSON FAMILY.
Marilyn has somehow fallen into motherhood and spent four decades married to David, who's pretty certain he loves her more than anyone has ever loved another person. Wendy, their eldest, a cause for concern, soothes herself with drink after being widowed young,while Violet, lawyer-turned-stay-at-home-mother, is disturbed by the reappearance of a son placed for adoption fifteen years earlier. Liza, a professor, is pregnant with a baby she's not sure she wants by a man she's not sure she lovesand Grace, their dawdling youngest daughter, lives a lie that no one in her family suspects.