A common adage about great screen acting is that it’s less about doing than being. Alfred Molina and John Lithgow provide a master class in that subtle, sublime endeavor in “Love Is Strange,” a delicate, superbly crafted and deeply moving portrait of family in its many forms and emotional permutations.

Ben (Lithgow) and George (Molina) have been together for almost 40 years when they are finally able to get married. “Love Is Strange” opens on their wedding day, during which they’re toasted by, among others, Ben’s nephew’s wife, Kate (Marisa Tomei), who raises a glass to the inspiration of their commitment to each other and to how much they’ve taught her and her husband, Elliot (Darren E. Burrows), about staying together over the long haul.

It’s a moving encomium, but it will be put to the test once “Love Is Strange” gets underway. Throughout this quiet but acutely observed drama — gently spiked with moments of warm, knowing humor — Ben and George will not only find their nascent union somewhat challenged, but will confront the very limits of their loving extended clan, genetic and chosen.

It’s not fair to go into much more detail about the plot of “Love Is Strange”; suffice it to say that it deals with many of the same themes and problems — with similar astuteness and sensitivity — as “Please Give,” Nicole Holofcener’s wise and funny comedy of manners set against the bemusing backdrop of Manhattan real estate. (One of the funniest running gags in “Love Is Strange” is the way Ben and George’s Manhattan friends disdainfully say the word “Poughkeepsie” when someone brings it up as a living option, as if it’s simply too outré to contemplate.)

Much as his characters do, Ira Sachs, who has directed the film from a script he wrote with Mauricio Zacharias, makes New York something of its own character here, filming affectionate shots of the city’s skyline with the same subdued tones that Ben uses in the painting he’s working on from Kate and Elliot’s rooftop.

Ben (John Lithgow) finally marries his longtime partner, George, but other family relationships show strains in “Love is Strange.” (Jeong Park/Sony Pictures Classics)

Sachs, who made the observant romantic drama “Keep the Lights On” two years ago, has both upped and deepened his game with “Love Is Strange,” somehow managing to capture life at its most quotidian, irritating and endearing while injecting the film with a subtle sense of outrage and impending unease. Although Ben and George seem rock-solid — an impression bolstered by Lithgow and Molina’s utterly convincing, two-spoons-in-a-drawer physicality with one another — viewers may well wonder where this small but pivotal chapter in their lives will lead them. The same questions surround Kate and Elliot’s son, Joey (Charlie Tahan), whose adolescent preoccupations don’t always jibe with having Uncle Ben in such close proximity.

Filmed in a series of beautifully arranged vignettes, set to a gorgeous classic soundtrack of mostly Chopin piano pieces, “Love Is Strange” wends its way to a shattering final moment, all the more stunning for the film’s most important events having happened off screen.

“Love Is Strange” turns out to be a subtle, sidelong coming-of-age and letting-go-of-age story, a lyrical ode to longing and passion that were there all along, had we only noticed. Attention is duly paid in this tender and touching film; the strangest thing about “Love Is Strange” is how completely un-strange it is, from its familiar family dynamics to its exquisite honesty and compassion.

★ ★ ★

R. At area theaters. Contains profanity.
94 minutes.