Portia Clemenza di Ebe is Romeo's mother, who reluctantly left him and the Montague name to live at a convent because she did not want to associate herself with the bloody and cruel ambitions of her husband. She's a kind, intelligent and understanding woman who prays for Romeo's happiness; she is the only one who greets him with a smile, which is why Romeo likes to visit her.

Just before the Flower Festival, Portia confirms Romeo's theory about Juliet being a member of the House of Capulet. She attempts to dissuade her son from experiencing tragic love but he boldly states his love for Juliet. She aids a distressed Juliet after the Montague attack on the Capulet restoration group, giving her shelter in the convent and expressing regret about the massacre of the Capulets. When Montague confronts her about Juliet or Romeo, Portia refuses to disclose any information, and he leaves her alone in the convent. Before the final raid on Montague, Romeo comes to her and apologizes in advance for drawing his sword against his father. She asks if that is the path his love must take but he leaves her unanswered.

(Souce: Wikipedia)