He built an apartment over his father’s house with his own money; do the heirs have any right to it?.

My father died in 1991 and left behind a house composed of three
floorsand a tailor's shop. I have a brother, three sisters and my
mother. My father promised the third floor to my brotherand he
promised the shop to me, but these words were not written down. I came
out of the Army in 1992 and I had some money, approximately 10,000
pounds, with which I built an apartment on the fourth floor, and I
helped my sisters to finish their education and get married. My mother
and one of my sisters help me in the shop by making buttonholes,
sewing on buttons and so on. My question is: how should the estate be
divided, based on the above information
Praise be to Allah.
Firstly:
Fathers are obliged to treat their children fairlyin terms of giving
gifts; it is haraam for a father to show preference to one of his
children in any way. Based on that, it would not be permissible to
fulfil the promise that he made toyou and your brother if he were
alive. As he has died, what is required is to divide the estate
according to the shares stipulated in sharee'ah. The scholars of the
Standing Committee were asked:
Is it permissible for a father to register a pieceof farmland in the
name of one of his sons and ignore the rest of his children? My father
registered a piece of farmland in my name and ignored my sister and
little brother. Should I sponsor these children or ignore them?
They replied:
The father is obliged to treat his children equallyin terms of giving
gifts, in accordance with the shar'i guidelines on inheritance. It is
not permissible for him to single out some of them and not others,
because the Prophet (blessings and peace of Allah be upon him) forbade
that. It was narrated from an-Nu'maan ibn Basheer(may Allah be pleased
with him) that his father brought him to the Messenger of Allah
(blessings and peace of Allah be upon him) and said: I have given this
son of mine a slave I owned. He said: "Have you given a similar gift
to all your children?" He said: No. He said: "Then take it back."
Agreed upon.
Based on that: your father must be fair in thegifts that he has given
tosome of his children by giving each of his children something like
that which he gave to the one mentioned, or else he should take back
the gift from him. As your father has died, you should divide the
estate between you and the rest of the heirs in accordance with the
shar'i ruling.
Shaykh 'Abd al-'Azeez ibn Baaz, Shaykh 'Abdullah ibn Ghadyaan. Shaykh
Saalih al-Fawzaan, Shaykh 'Abdal-'Azeez Aal ash-Shaykh,Shaykh Bakr Abu
Zayd
End quote from Fataawa al-Lajnah ad-Daa'imah, 16/216
For more information, please see question no. 114659
Secondly:
With regard to the apartment that you builtwith your own money,
itbelongs to you and the heirs have no right to it. When the estate is
divided, this apartment should be evaluated on the basis that it is a
separate apartment, with no share of the value of the land, and is
your property. In other words, experts should work out the value of
this structure without including any part of thevalue of the land on
which it is built.