Who are the two Rightly Guided Caliphs who married daughters of Ali ibn Abi Talib (may Allah be pleased with him), and what is the significance of this marital relationship?

The Ahlus-Sunnah wal-Jama'ah, the companions of the Prophet, peace and blessings be upon him, and his household, hold them in high regard and draw closer to Allah through their love. The relationship between the Companions and the Prophet's household was based on love and respect, extending to intermarriage. Examples include the marriage of Umm Kulthum, daughter of Ali, to Omar ibn Al-Khattab; the marriage of Hussein ibn Ali to Hafsa bint Abdur-Rahman ibn Abi Bakr As-Siddiq; and the marriage of Umm Farwah bint Al-Qasim ibn Muhammad ibn Abi Bakr As-Siddiq to Muhammad Al-Baqir, which led Jafar As-Sadiq to proudly state, "Abu Bakr bore me twice." These marital ties demonstrate the bonds of kinship and love between the Prophet's household and the Companions, contrary to the animosity and discord claimed by the Rafidah. The Companions were "merciful among themselves," and Abu Bakr said, "By Him in Whose Hand my soul is, the kinship of the Messenger of Allah, peace and blessings be upon him, is dearer to me to maintain than my own kinship." Thus, the alleged animosity has no basis.