Praise be to Allaah.
What you must do is to divide the estate of your
grandfather to all his heirs as commanded by Allah, may He be exalted,
with each male getting the share of two females.
If your father paid any of his own money during the building
of the house, attention should be paid to that when dividing the estate. The
same applies if you paid anything of your own wealth when buying the other
This division of the estate is not only required to discharge
the duty of your father; rather it is also required to discharge your duty
too, because now you are living in what you do not possess and you are
transgressing against the rights of others unlawfully. You are not entitled
to anything of this house apart from your father's share of it.
The same may be said concerning the house in which your
paternal aunt is living; she is not entitled to anything of it apart from
her share of her father's estate.
To sum up: you have to work out your grandfather's estate and
divide it among his heirs, who are your father and his four siblings. Beware
of wrongdoing and consuming haraam wealth and living in an ill-gotten house,
because that leads to grievous consequences and a bad
We ask Allah to protect you and help you to restore rights to
the people who are entitled to them.
And Allah knows best.