How can I advise my mother and sister, who wear the niqab but expose their feet and hands, and my sister wears patterned abayas? Is this considered tabarruj (immodest display)? And is it permissible to agree to accompany them outside the home while they are in this attire, especially since they ask me to and watch TV series despite knowing they are forbidden?

Scholars differ regarding the 'awrah ( منطقة في الجسم يجب سترها ) of a woman's hands and feet. The preponderant view, in our opinion, is that a woman's feet are considered 'awrah and must be covered from non-mahram (definition) men. This is the view of the majority of scholars, and it also applies to her hands.

You should advise your mother and sister gently and wisely about the obligation of covering their feet and hands.

If your mother insists on uncovering her hands and feet, there is no harm in accompanying her to the market if she asks you to, as this issue is not a matter of consensus, and obeying her is obligatory in matters that do not involve disobedience (to Allah).

As for television series, your mother and sister must comply and abstain from disobeying Allah as long as they know of their impermissibility. You should advise them and remind them of Allah.