Arthur, Kenneth and Donald Foster are brothers and partners in a small home building firm in Northern Virginia who say they conduct ehir day-to-day operations on a unanimous basis. If one brother doesn't agree to something, they don't do it.

"Sometimes it takes a little longer to get a decision but that's the way they operate and its seems to have worked well for 14 years," one observer said.

Natives of Northern Virginia, the Fosters founded Forster Brothers, Inc., in 1963. They all attended the University of Virginia and each is the father of three children. Th

Arthur E., 42, the firm's President, has a BA in engineering and an MA in business administration. He handles land planning and acquisition, financing and (co-ordinates) legal and engineering work.

Kenneth E., 40, is vice president and is in charge of construction and purchasing. His degree is in mechanical engineering and he previously worked as a carpenter. He is also overseeing the construction of a new house in Fairfax County for his own family; his brothers already live in Foster-built custom houses in Fairfax.

Donald E., 39, is vice president and secretary of the firm. He's responsible for new home subdivision sales, general brokerage sales (a new division opened recently), customer service and processing through the county government.

Currently Foster Brothers, Inc. is building detached houses at the 375-lot Long Branch subdivision in the Annandale area and at Middleridge (500 lots), also in Fairfax County. The houses are priced in the $70,000s and $80,000s. The firm has a small, 66-unit town house project in Fredericksburg, Va.

Another project, the four-story Chess & Foster office building in Fairfax City, is scheduled for completion this fall. The firm, which also includes marketing director Gregory R. Cox and two secretaries, will move there from leased space in Vienna.

Two project superintendents work on each active building job: one on front (or beginning) construction and the other on finishing.

The Fosters' expect to complete 150 single-family houses this year - a total of $12 million in construction - in addition to the Fredericksburg town houses.

If the brothers Foster are unusual (and they'd be the last to say that they are), it's because they have been low-profile, home building practitioners with a record of durability.

One Foster-watcher describes them as "meticulous about everything they do." Another Foster friend commented: "There's no jealousy among them. Each has a separate responsibility but they make all decisions on a common basis. And they really seem to like what they're doing."