Is it obligatory to declare Sufi relatives who commit major shirk based on their own interpretations as kafir, given that they do not know the Arabic language and do not read the Quran, bearing in mind that a Muslim is not excused for major shirk if he is able to read the Quran or ask scholars?

A Muslim must achieve Tawhid (monotheism) and follow the Quran and Sunnah according to the understanding of the Salaf (pious predecessors), while avoiding innovations (bid'ah) and Sufi orders. It is impermissible to declare a Muslim a disbeliever (takfir) or a transgressor (tafsiq) except with proof from the Quran and Sunnah, and only after fulfilling the conditions for takfir and ensuring the absence of its impediments, such as ignorance or misinterpretation (ta'wil). The fundamental principle is that a Muslim's Islam does not vanish merely due to suspicion until the conclusive proof of the prophetic message (al-hujjah al-risaliyyah) is established against him and his excuse is exhausted. Many people grow up in environments where much of the knowledge of the prophecies is absent; such an ignorant person is not deemed a disbeliever until what the Messenger brought reaches him. The questioner must invite his relatives and acquaintances to Tawhid and the Sunnah, and be patient with them.