What is the ruling on my behavior towards my parents and the estrangement of my sister due to her causing my parents and siblings to alienate me?

The questioner is advised to be diligent in maintaining ties with her parents and relatives, to be gentle with them, and to clarify facts to them in a kind manner, or through someone who holds influence with them. If they insist on severing ties, then you and your children should not cut them off. Maintain connections with them in any possible way. If you fear harm from visiting them, then connect with them via phone or any other means. As for the sister who caused strife, she should be advised and reminded of Allah. If she persists, then there is no blame in shunning her if a legitimate benefit necessitates it, while being cautious not to accuse people based on speculation.