When a brother has a sister who lives in her own place, who isnt practising and thinks its okay to be alone with a man despite advice from her brother and family. Should the brother be in the presence of his sister as much as he can, when the sister is alone with the man? What else should her brother do to express protective jealousy? Thanks
What she is doing is haram. He is not mahram to her hence she should not communicate with him. If she is not listening to you then you should involve your parents before something extreme happens. If your parents are not willing to interfere, being with them doesn’t seem to work all the time as you can’t be with her 24/7. You must remind her of Allah and show her the magnitude of such sins.