Olivia Shelltrack and Fondrey Loving were denied an occupancy permit after moving into a home in this St. Louis suburb because they have three children and are not married.
The town's planning and zoning commission proposed a change in the law, but the measure was rejected Tuesday by the city council in a 5-3 vote.
"I'm just shocked," Shelltrack said. "I really thought this would all be over, and we could go on with our lives."
Mayor Norman McCourt said starting Wednesday the city will begin trying to evict groups who do not fit into Black Jack's definition of family, reports CBS affiliate KMOV-TV in St. Louis.
The current ordinance prohibits more than three people from living together unless they are related by "blood, marriage or adoption." The defeated measure would have changed the definition of a family to include unmarried couples with two or more children.
McCourt declined to be interviewed, but said in a statement that those who do not meet the town's definition of family could soon face eviction.
In the statement, McCourt said, "the city provides information about its occupancy permit requirements to anyone who requests it. ... As mayor, I am required by state law to uphold the laws of the city of Black Jack."
Black Jack's special counsel, Sheldon Stock, declined to say whether the city will seek to remove Loving and Shelltrack from their home.