For those who have read classical Greek literature, the story of Oedipus is something that is very stark; inspite of all the efforts to prevent it, the son finally ends up marrying the mother. His family knew of a prophecy that warned of this, and they sent him away when he was a baby so that he could be killed. However, he survived and lived at another king's court; and the prophecy finally came true later when killed his real father in a roadside argument, and then, in another twist of fate, married his mother. When they found out the truth, his mother killed herself and he blinded himself.
In this case, the Brazilian couple were both abandoned at birth. They continued their efforts at individually finding their birth families, When the wife finally found her mother, she also learned to her horror, that her husband had the same mother and hence they were also brother sister. However, in this case, they have accepted their fate and decided to make a success of their marriage (link to article)
Adriana and Leandro, a Brazilian couple, both abandoned by their mothers in childhood, spent their lives anxiously searching for their mothers. They couldn't have imagined in their wildest dreams what their search would lead to. The couple knew that their mothers shared the same name, Maria, but thought it was just a coincidence. When Adriana decided to step up her search, she joined the 'Angel of Meetings', a daily broadcast on Brazilian radio station Radio Globo promoting the reunion of people with relatives and friends who are no longer in contact. Little did she know what was in store for her family.