Theirs is a storybook romance, from the time they became friends in the fourth grade to a love affair that blossomed when they were in their late 30s. Now in a legal union, Ana Leiderman and Veronica Botero have a young son and daughter. But they are not quite a family under the law. Leiderman, who gave birth after being artificially inseminated, has custody of the children. And Botero has virtually no rights, or legal responsibilities, concerning them.