Is it permissible for one of the parents to perform the Hajj pilgrimage if there are children in secondary school, and to what extent can the uncle intervene to guide his brother's sons and daughters religiously and educationally in the event of parental negligence?

An uncle's care and attention to his brother's children, from a religious and ethical standpoint, is commendable. A Muslim is asked to offer advice to those closest to him first, for Allah commanded His Prophet Muhammad, peace be upon him, to "warn your closest kindred." An uncle does not have direct guardianship over his brother's children if their father is alive, so he cannot treat them with the same strictness as his own children, but he is more responsible for them than for strangers. There is no impediment to either parent performing the Hajj pilgrimage, as the mother needs a mahram, and the father must provide for the expenses and enjoin religious adherence. Parents must raise their children to obey Allah and avoid sins, for religion is the most important factor for happiness in this world and the hereafter. The uncle must be careful not to treat his brother's wife as if she were one of his mahram relatives.