As-salam-alikum, My uncle's ex-wife has left Islam and joined a cult-like religion. She is very involved in the religion and has taken her kids (my cousins who are in their 20s) with her. I feel terrible that my cousins are involved in this cult. They work for this group and live with them. Their cult is vey controlling and has brain-washed them. All of my relatives have cut off contact with them. My cousins and aunt live in the same region as I do. I would like to maintain contact with them and invite them to my house on weekends. I feel that maybe if they see what Islam has to offer they might insha-Allah come back to Islam. They have a very distorted image of Islam and think it is backward religion. Is it allowed to maintain contact with people who have consciously left Islam and accepted another religion? My Iman Al-humd-durillah is strong and Insha-Allah I will never abandon Islam. I am thinking that this might be dawah as they have shown interest in maintaining contact with me and I might be able to slowly have some influence on them.

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 is His slave and Messenger.

It is permissible for you to keep ties with the wife of your uncle and your cousins who apostated from Islam with the purpose of inviting them to Islam provided you have enough knowledge to invite them to Islam and repel their misconceptions. You should observe Hijab when speaking with your cousins and not talk to them in a soft or attractive manner, and you should not stay in seclusion with them. If there are men who may call them to Islam, then this is better. 

We ask Allaah to enable you to do what pleases Him and reward you for inviting people to Islam.

For more benefit on how to invite an apostate back to Islam, please refer to Fatwa 87672.

Allaah Knows best.