You're right about Rabbit Hole being about a boy who dies, but there is a troubled central relationship in that play between a mother and daughter (played on Broadway by Tyne Daly and Cynthia Nixon) so I think it does qualify as the kind of play the initial poster was looking for.
Picnic (to a certain extent) Only When I Laugh A Delicate Balance Mourning Becomes Electra The Little Foxes Six Degrees of Separation
"The gods who nurse this universe think little of mortals' cares. They sit in crowds on exclusive clouds and laugh at our love affairs. I might have had a real romance if they'd given me a chance. I loved him, but he didn't love me. I wanted him, but he didn't want me. Then the gods had a spree and indulged in another whim. Now he loves me, but I don't love him." - Cole Porter