Is a grown son obligated to care for his family after his father's death, and will he be held accountable for their not praying, and is he required to enforce the niqab and prohibit television for them, given that he is in the early stages of his religious commitment?

A person must repent to Allah, fulfill their obligations, and abandon prohibitions. Taking care of his mother and sister is obligatory upon him by providing for them if he is able and they possess no wealth. It is not obligatory for him to compel them to fulfill obligations or prevent them from prohibitions; rather, such care should be through advice, guidance, bringing benefit, and averting harm. Changing the reprehensible is obligatory upon him according to his ability, by hand, tongue, or heart.