Sayyed Mohammad Al-Musawi, Sayyed Mohammad al-Musawi is originally from Iraq and heads up the World Ahlul Bayt Islamic League in London. Other than being involved in various humanitarian projects, he frequently responds to... Answer updated 2 years ago

Any phrase in the will which contradicts the Sharia rules is simply invalid. No father or mother or grandfather etc, can exclude females from the will. In your question, the daughters remain the owners of their rights in inheritance according to Islamic Sharia and no one is allowed to take any thing from their right under any title or excuse. 

Inheritance share can not be prevented unless the person has changed his/ her religion away from Islam, or killed or took part in killing the deceased person.