The will written by your father cannot be enforced during his life time. He can change the will anytime during his life time.
If the property is his self acquired property or he is the absolute owner of the property he may make the bequest in any manner as per his own wish and desire and to anyone of his choice. No one can demand or put pressure on him to allot a share to them, that would be an illegal act and punishable under criminal law for the offences of criminal intimidation and threats etc.
Neither your sister's husband nor your sister nor anyone in your family or outside can file any cs against your father for not allocating a share to them, the same will not be tenable or maintainable.
During the subsistence of the present will, if your father breathes his last, the will shall come into force and in case of any dispute over it, you can apply for grant of probate of will through competent court of law and bring the will into force.