A state senator from East Flatbush who is running for Brooklyn district attorney, John Sampson, is caught in the crossfire of a bitter battle between two powerful families on the borough’s political scene.

A Democratic congressman from the borough, Major Owens, said he was rescinding his endorsement of Mr. Sampson yesterday and will back one of Mr. Sampson’s rivals, the former chief of Attorney General Eliot Spitzer’s anticorruption division, Mark Peters.

A Sampson campaign spokesman, Michael Cohen, said he was unaware that Mr. Owens had previously endorsed Mr. Sampson and declined to comment on the congressman’s endorsement of Mr. Peters.

Although Mr. Owens declined to give the specific reason for his about-face in the district attorney’s race, someone close to the congressman, speaking on condition that he would not be identified by name, said the endorsement switch stemmed from Mr. Owens’s feud with the Boyland family of Ocean Hill-Brownsville.

According to the Owens adviser, Mr. Sampson broke a promise not to provide any assistance to a retired state assemblyman, William Boyland Sr. According to Mr. Boyland, the state senator cooperated in the petition phase of his current City Council campaign. Mr. Boyland is one of 10 Democratic candidates vying to replace his term-limited daughter, Tracy Boyland, whose council district includes Ocean Hill-Brownsville, Bedford-Stuyvesant, and parts of East Flatbush.

In 2002, Mr. Boyland abruptly resigned from his Assembly post shortly after winning an 11th term. His departure forced a special election for the seat, in which his son, William Boyland Jr., prevailed. Yesterday, Mr. Owens also endorsed one of the senior Mr. Boyland’s rivals in the council race, community activist Darlene Mealy.

The congressman said the Boyland family is a “dynasty” that “believes it can rule indefinitely.”

But the senior Mr. Boyland, in a phone interview yesterday with The New York Sun, accused Mr. Owens of establishing a “twinkle-twinkle dynasty” of his own.

The congressman, who is retiring next year after 12 terms, has endorsed his own son, Chris Owens, in the race for the seat that he is vacating.

The senior Mr. Boyland said his daughter would again run for the House seat.

In the elder Mr. Owens’s final run for re-election in 2004, Ms. Boyland mounted a vigorous primary challenge, placing third in a four-candidate field with 22.5% of the vote. The incumbent congressman won the primary with 44.1%.

A City Council member from Flatbush, Yvette Clarke, also was among Mr. Owens’s challengers in 2004, placing second with 29.2%, and she, too, is now feeling the congressman’s wrath. Mr. Owens endorsed Ms. Clarke’s challenger in next month’s primary, Zenobia McNally.

Mr. Peters, Ms. McNally, and Ms. Mealy are among the eight candidates on the congressman’s Integrity Team – a slate the elder Mr. Owens unveiled at a press conference yesterday. The only candidate for citywide office on the slate is a constitutional lawyer who is running for public advocate, Norman Siegel.

In the four-candidate field for Brooklyn district attorney, Messrs. Peters and Sampson are challenging the 16-year incumbent, Charles Hynes. A former deputy commissioner of trials in the Koch administration Police Department, Arnold Kriss, also is running in the September 13 primary.