Should a young man in his twenties leave the Muslim Brotherhood in response to his mother's wish, as she fears for him and considers joining organizations to be partisanship that does not align with the principle that "religion is one"?

The children should advise their mother and explain that the existence of groups working to support the religion does not contradict the unity of the Ummah, and that the principle is for these groups to complement each other in embracing the various branches of the religion. As long as they rely on the Quran and Sunnah, participating in them is a great good and a form of cooperation in righteousness and piety. If the mother insists on preventing her son and he will not be harmed, then her obedience is not obligatory. It is preferable to deal with her gently and continue cooperating with his brothers without informing her.