Brotherly love takes many forms; in the case of Rob and Eric Brill, it’s a shared passion for modernism. Rob, the younger of the two and a rock musician, recently completed the second of two live/work homes in Los Angeles that serve as spaces for recording and rehearsing and as expressions of his taste for a bracingly spartan brand of minimalism. He built both homes with co-investment from his brother Eric, a retired businessman and serious collector of industrial design, who until recently lived in a 1934 Edward Durrell Stone house in New York State. “We are modernists,” says Rob, with the clarity of someone declaring a religious belief. “We love its simplicity, the embrace of its surroundings.” Along the way, though, the Brill brothers have been struck by another near-spiritual commitment: environmentalism.