In 1995, Bryan, a Democrat who had become disenchanted with the Clinton administration, even joined the Republican Party at the request of his older brother, who is legally blind, in order to serve as manager of his mayoral campaign.

Image Bryan Lonegan supports immigrant rights. Credit... Suzanne DeChillo/The New York Times

A decade later, the brothers became estranged when Bryan quietly quit the Republican Party — because of opposition to the Bush administration — in the middle of Steve’s losing primary campaign for New Jersey governor.

Since the rift, their political differences have widened, as immigration became a wedge issue in communities across the country.

“For the last two years, my brother’s been on an anti-immigrant kick,” said Bryan, reacting to Steve’s recent suggestion that the Bogota police be deputized as federal immigration agents. “He’s playing a very dangerous game, and he’s doing it for political points, not because it makes sense in the community, but because this is a way for conservative politicians to hold on to what they’re losing.”

Steve, a big, brusque, ruddy-faced man who was an all-state lineman at William Paterson University, seemed momentarily nonplussed when his brother’s views were relayed. But he quickly recovered his stride.

“People who are pro-illegal immigration say you’re fanning the flames if you don’t shut up and go along with what they want,” he said. “I’ll stand up for legal immigrants instead of abandoning our principles to let illegal aliens in the country to shoot people in the head.” He was alluding to the recent schoolyard killings in Newark, in which two of the men accused in the three murders were suspected of being in the country illegally.

To some people, how these brothers ended up on opposite sides of the immigration debate may seem like less of a mystery than how they stayed close for so long.