It is narrated from Ja'far bin Muhammad (may Allah have mercy on him) that Hasan and Husayn (may Allah be pleased with them both) used to pray behind Marwan. Imam Shafi'i (may Allah have mercy on him) says, Hatim bin Isma'il asked: "Did they not come to their homes and (repeat) the prayer?" So Ja'far (may Allah have mercy on him) said: "No, by Allah, they did not add to the prayer of the imams."
Hadith Referenceمسند الإمام الشافعي / كتاب الصلاة / 298
Hadith Takhrijاخرجہ ابن ابی شیبہ: 7559، والبئیقی: 3/222، وفی معرفة السنن والآثار لہ: 1541۔