Meanwhile Cosima was having a love affair with Richard Wagner . In 1868 she left her husband to live with Wagner , taking their daughters with her . However , his wife Cosima , who had been carrying on an extramarital affair with Richard Wagner for some time , left him in 1868 , taking with her two of their four daughters , Isolde and Eva -- the two whom Richard Wagner had fathered -- and in 1870 divorced BÃ 1\/4 low .