The Most Fun We Ever Had by Claire Lombardo

In this “rich, complex family saga” (USA Today) full of long-buried family secrets, Marilyn Connolly and David Sorenson fall in love in the 1970s, blithely ignorant of all that awaits them. By 2016, they have four radically different daughters, each in a state of unrest.
 
Wendy, widowed young, soothes herself with booze and younger men; Violet, a litigator turned stay-at-home-mom, battles anxiety and self-doubt; Liza, a neurotic and newly tenured professor, finds herself pregnant with a baby she's not sure she wants by a man she's not sure she loves; and Grace, the dawdling youngest daughter, begins living a lie that no one in her family even suspects.
 
With the unexpected arrival of young Jonah Bendt—a child placed for adoption by one of the daughters fifteen years before—the Sorensons will be forced to reckon with the rich and varied tapestry of their past. As they grapple with years marred by adolescent angst, infidelity, and resentment, they also find the transcendent moments of joy that make everything else worthwhile.