From NetFlix:

Small-town single mom Sammy Prescott (Laura Linney) is preoccupied
with raising her son Rudy (Rory Culkin), who’s become sullen — and
curious about his missing dad. Amid romantic and work troubles,
Sammy’s wayward brother Terry (Mark Ruffalo) appears, instantly
bonding with Rudy and instigating a perilous father-son reunion.
Director Kenneth Lonergan’s intimate, Oscar-nominated drama
won the Sundance Film Festival’s Grand Jury Prize.

MarkRuffalo does a great job. Ends with a scene that for me was
very sad. Nevertheless, a real feel-good.