All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
Enjoining good and forbidding evil are obligatory on every Muslim, for the Prophet, sallallaahu ‘alayhi wa sallam, said that offering advice is one of the essential pillars of Islam. [Muslim]
Thus, we warn the questioner against being indifferent and against refraining from advising her relatives and guiding them. If they listen to you and respond positively, this will be great. However, if they persist in their wrongdoing, you may not keep sit with them, unless this does leads to worse consequences. Not sitting with them and deserting them is not considered severing ties of kinship.
Allaah Knows best.