I am 21 years old and I am just confused about some irritating behaviour of my husband and I want to know if they are permissible in Islaam. My husband always touches his sister's buttocks and stomach. She is 19 years old. He also speaks filthy words with her.
Note that my husband prays 5 times a day and keep fast ........and he tries to be a practicing Muslim. But his sister doesn't believe in this at all. That's why she never forbids him to do all these things. Even she loves to be like western people. She always tries to show him western movies and doesn't mind if he sees girls wearing swimming costume. So is it permissible for him to touch his sister in such places? Also inspite of being a practicing Muslim should he show such behaviour in front of his family which only believe in Allaah not in the ruling of Qur'aan? Also I don't mind if he loves his sister rather I think his sister has a right over him. And if she falls in danger I always want to help her. But I think if a brother touches his sister such way then it seems that he is doing that to get benefit from her.

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. We ask Allaah to exalt his mention as well as that of his family and all his companions.

Undoubtedly, what your husband is practicing with his sister is forbidden even if there is no sexual desire. These actions and exchange of filthy words show shamelessness and vulgarity. So, He has to make repentance from those shameless acts.  Allaah says (interpretation of meaning): {He [i.e. man] does not utter any word except that with him is an observer prepared [to record].}[50:18]. Allaah also says (interpretation of meaning): {…you [people] do not do any deed except that We are witness over you when you are involved in it….}[10:61].  He has to be ashamed of Allaah who watches him and his actions as well.  If the family of your husband or his sister are not Muslim then he has to avoid having affection for them.  Allaah says (interpretation of meaning): {You will not find a people who believe in Allah and the Last Day having affection for those who oppose Allah and His Messenger, even if they were their fathers or their sons or their brothers or their kindred…..}[58:22].

As for your saying 'your husband's family believe in Allaah but do not believe in rulings of Qur'aan', whoever rejects the rulings of Qur'aan is a disbeliever.  How can one be considered Muslim if he does not believe in praying, fasting, etc. as being obligations?

Dear sister, know that the reason for shamelessness, lack of religiousness, negligence of Islamic rulings and following western culture, is living amongst non-Muslims and staying in their communities which are full of disbelief, evil and immorality.  The Prophet who did not speak except what was revealed to him was truthful when he said: "Whoever socializes with a polytheist and resides with him is similar to him." [Abu Daawood]

So, you have to exhort your husband gently, and wisely remind him of Allaah who knows what penetrates into the earth and what emerges from it and what descends from the heaven and what ascends therein.