ATLANTA (AP) _ When Jim Zauderer went to the City Council to seek repeal of a gay rights ordinance, his brother publicly announced to the meeting that he is gay.

Doug Zauderer, 35, describes himself as ''a very low-profile,'' non- political person who probably would not have spoken out Monday night except for a newspaper ad purchased last week by Citizens for Public Awareness, a group headed by his brother.

The $9,100 full-page ad in The Atlanta Journal and The Atlanta Constitution attacked the ordinance intended to protect homosexual city employees from discrimination and asked, ''Why should our city government condone homosexual sodomy when it is illegal in the state of Georgia?''

After learning of the ad and an appearance by his brother on television urging repeal of the ordinance, Doug Zauderer, who is a florist, said he called the Atlanta Gay Center and offered to speak at Monday's hearing.

''I was flabbergasted, embarrassed and ashamed,'' he said of his brother's actions.

Jim Zauderer, 32, who is campaign treasurer for Joseph Morecraft III, Republican candidate in the 7th District congressional race, has declined to discuss his relationship with his brother. He says only that supporters of the ordinance have failed to cite a single case of homosexuals being discriminated against in Atlanta and contends that the ordinance therefore should be repealed.

Doug Zauderer, who was best man at his brother's wedding, said their relationship has cooled steadily since he told his family about a dozen years ago of his homosexuality.

His father suggested hormone treatments, while his brother suggested counseling, Doug Zauderer said.

''I never could explain to them that I was born gay, that it is nothing a person chooses to be, that it is similar to being born left-handed or liking steak well done rather than rare,'' he said.