Not starting to fast when Ramadan commences claiming that a Shaykh has not commanded

Q: I have some relatives who do not start their fast with us when Ramadan commences, claiming that one of their Shaykhs in Makkah has not commanded them to start the fast. Thus, they may delay their fast for one or two days after us. They have been approached with advice in order to follow the community in the beginning of the fast, but they still insist on their practice. Their excuse is that their Shaykh has not yet commanded them to start fasting and he has not sighted the new moon.My question, Your Eminence, is: Can the sighting of the new moon be established by the witness of one man, two men, or more? What is the ruling on the fast of those people? Should I maintain good relations with them or desert them? And what is the ruling on my dealing with them and keeping good relations with them? Please give us Fatwa regarding this, may Allah reward you with the best, and may Allah benefit everyone with your knowledge.

A: The Prophet Muhammad (peace be upon him) said: Observe the fast when you see it (the new moon), and break the fast when you see it (the new moon). If the sky is overcast, then calculate it (the months of Sha'ban or Shawwal as thirty days.) In another narration, he (peace be upon him) said: Then complete the month of Sha'ban as thirty days. Therefore, it is incumbent upon them to start their fast with other Muslims, and it is not allowed for them to differ with the Muslims under the pretence that a person (Part No. 9; Page No. 15) has not yet commanded them to begin fasting. There is no obedience to a human if it entails the disobedience of the Creator. The Messenger (peace be upon him) commanded us to fast along with other Muslims in the community. He (peace be upon him) stated: Sawm (Fasting, i.e. beginning of Ramadan) is the day when you start Sawm, and Al-Adha (the Feast of the Sacrifice) is the day when you sacrifice. He (peace be upon him) also said: Keep firmly attached to the Jama`ah (the Muslim main body which follows the Qur'an and Sunnah), for the Hand of Allah is with the Jama`ah, and anyone who breaks away from it will be cast in Hellfire. Moreover, it is not a condition that everyone must sight the new moon in order to start fasting. If it is sighted by just one person, then it becomes an obligation upon everyone to start the fast. When Ibn ‘Umar (may Allah be pleased with him and his father) told the Prophet Muhammad (peace be upon him) that he had sighted the new moon, the Prophet (peace be upon him) commanded all people to start the fast.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.