Os Gemeos grew up in Sao Paolo, where they absorbed an ethic of improvisation — a defining characteristic of their work even now — and a love of Brazilian traditional dress and patterning. They discovered American hip-hop culture in the mid 1980s.

It all depends on your perspective. After all, one man’s cultural ruin is another man’s restoration of law and order. But it’s an interesting moment in the evolution of the street art phenomenon from “urban blight” to institutional co-option.

Does such art-world recognition inevitably entail the domestication of all that makes street art dangerous and interesting? Does it signal an end of things, even a whiff of cultural ruin?

Like Faitakis and America’s Barry McGee and Shepard Fairey, who all started out as street artists, Os Gemeos are now feted in the contemporary art world, requiring that they straddle a sometimes awkward divide: between the prestige (and oftentimes the pretension) of contemporary art and the edginess (and oftentimes the illegality) of street art.

Another is on the façade of the Revere Hotel Boston Common a few streets away, and a third — a collaboration with artists RYZE, Todd James, and Caleb Neelon — is on the wall of Mama Gina’s restaurant in Union Square, Somerville.

The largest covers the exterior wall of a giant air intake structure on the Rose F. Kennedy Greenway. It’s by far the most successful piece of public art I’ve seen in Boston in the more than four years I’ve lived here.

Otavio Pandolfo and his brother Gustavo, who call themselves Os Gemeos (Portuguese for “the twins,” which in fact they are), are street artists from Brazil. They have a sprightly, one-room show at the Institute of Contemporary Art, which is complemented by three murals around the Boston area.

Given our location — a 10-minute walk from the Acropolis — and Greece’s current economic plight, I thought this was wonderfully droll.

Stelios Faitakis, for instance — a Greek artist who combines a Byzantine visual idiom with hot political content — had a mural prominently placed at the last Venice Biennale, and now has a flourishing career on the international contemporary art circuit. But at the opening I attended, two short blocks away from Faitakis’s earliest extant mural (now just a weather-beaten fragment), an art critic I spoke to insisted that the “golden age” of street art in Athens had ended 10 years ago. “You are among the ruins!” he concluded with a flourish.

In Athens earlier this year I attended the opening of an improvised gallery space for street artists. Athens’s built environment is covered in graffiti — predominantly hastily scrawled tags, but also ambitious, colorful, and often large examples of public art. Many of these works are very prominent, and some of the artists responsible have made names for themselves, both inside Greece and, in one or two cases, internationally.

“Wild Style,” an influential film about hip-hop, was a big early influence, reports curator Pedro Alonzo in the exhibition catalog. So was the humorous and socially critical work of McGee, one of the first graffiti artists to use figurative imagery in his work. McGee contacted the twins on a trip to Brazil in 1993.

The Os Gemeos show is the latest in a series of shows the ICA has dedicated to popular street artists, including Fairey and the Mexican tattoo artist Dr Lakra. (McGee is to be the subject of an upcoming show.) Fairey, in particular, proved controversial, and so already have Os Gemeos. A local television news segment about their Greenway mural included interviews with members of the public who thought the mural resembled a terrorist or “Bart Simpson in a Mujahideen outfit.”

Nice, but slightly off the mark. It actually shows a boy in patterned pajamas, huddled up against the edges of the giant wall. Yes, he also wears a shirt wrapped around his head, mouth and nose; but many of Os Gemeos’s unwaveringly cute characters wear similar headwear.

The face covering, of course, is obligatory street artist gear, originally adopted both to protect the airways from spray paint fumes and, like the similarly ubiquitous hoodie, to conceal identity (spray painting is, at least in its illegal forms, necessarily a hit-and-run affair). Now it’s a symbol: a sign of tribal belonging as much as an emblem of urban defiance.

What I love about the mural is the way it takes possession of its site so confidently and, in doing so, completely transforms it. Unlike the modernist abstract steel sculptures one routinely sees in gray and disconsolate corporate plazas, this is an intervention that feels entirely unexpected and frankly joyous. It stirs the heart and — in its play with color and scale — it’s wonderfully witty.

It also has a slightly disturbing edge: Why is the boy huddled like that? Could it be that he is a fearfully defiant street kid hiding from nearby police? If so, his inflated scale and vivid coloring combine to trigger the classic street-artist challenge: Just whose city is this?

But such questions are, finally, rhetorical. They are effectively sidelined by Os Gemeos’s delirious patterning and cartoony drawing — and by the palpable civic chutzpah the piece embodies. (Just think of all the draining meetings with mayoral staffers, law enforcement officials, museum curators, and corporate sponsors required to pull off a commission like this! No wonder fans of street art look back with nostalgia upon a putative golden age!)

The ICA show adds depth and complexity to our view of these artists. A few of the works in it are a little on the twee side. But they make it easy to see why these twins are now, as Alonzo puts it, “the face of the Brazilian graffiti movement.”

The best of the works manage to be both ironically knowing and sincerely openhearted. They are full of trompe l’oeil effects and other shifts in visual register, from stenciled patterning to conventional perspective and even relief carving.

There is a children’s picture book quality to much of what they do — an impression cemented by their signature yellow, skinny limbed protagonists. And one could perhaps argue that the fundamental requirements of successful street art (recognizable style, ubiquity, repetition) can feel like fetters on genuine creative expression: that these things should be, if anything, byproducts, not explicit ambitions.

But what is exciting about Os Gemeos is that, starting gleefully from within the parameters of street art, they are constantly busting out of those parameters.

If (and I don’t really buy this) their institutional acceptance signals the ruin of a genuine — and genuinely oppositional — street aesthetic, so be it. Ruins can still be enthralling, and of lasting fascination. After all, people still seek out Lord Byron’s graffiti on the ruins of the Temple of Poseidon, just outside Athens.

Sebastian Smee can be reached at ssmee@globe.com.

Correction Because of a reporting error, this story about Brazilian artists Os Gemeos misspelled the name of the street artist RYZE, and mischaracterized the residences of RYZE and fellow street artist Todd James. They live in New York.

© Copyright 2012 Globe Newspaper Company.