Impermissibility of a son taking from his father's money without his knowledge if he does not give equal grant all his sons
If your father allowed you, as he did with your brothers, to take from his store whatever you need for yourself and your family even without informing him; it is permissible for you to do so. On the other hand, if your father helped your brothers in their marriages; it is Wajib (obligatory) for him to provide similar help to you. Proof for the foregoing is a Hadith which is narrated on the authority of
Al-Nu`man ibn Bashir (may Allah be pleased with them both):
That his father brought him to the Messenger of Allah 'peace be upon him' and said: 'I have donated this slave of mine to my son.' (Part No. 16; Page No. 232) Allah's Messenger 'peace be upon him' said: 'Have you donated to every one of your sons like this?' He said: 'No'. Thereupon Allah's Messenger 'peace he upon him' said: 'Then take him back.'
In another narration: Allah's Messenger 'peace be upon him' said:
'Have you done the same with every son of yours?' He said: 'No.' Thereupon he (the Holy Prophet) said: 'Fear Allah, and observe equity with your children.' So my father returned and took back the gift.
Another narration reads: Allah's Messenger 'peace be upon him' said:
'O Bashir, do you have other children besides this son' (i.e. whom you gave a gift)? He said: 'Yes.' The Prophet then said: 'Have you given them all like him?' He then said: 'No.' Thereupon, the Prophet said: 'Seek another person to be a witness to that, for I am not to be a witness to an unjust act.'
Another narration states:
'Do not make me a witness to injustice.'
Another narration reads:
'Call someone else besides me as a witness.' And he further said: 'Would it please you that they (your children) should all behave virtuously towards you?' He said: 'Yes.' He (the Prophet) said: 'Then don't do that' (i.e. Don't give a gift to one to the exclusion of others).
(Agreed upon by Al-Bukhari and Muslim).
If you find that your father is neglectful of your rights in comparison to your siblings, ask him politely and softly to give you your due rights and clarify to him that applying
Justice amongst Children is Wajib according to Shari`ah (Islamic law). Finally, if your father complies with the foregoing then all praise be to Allah Alone. Otherwise, it is impermissible for you to take from his money to make the repairs that you mentioned in the question. You have to exercise patience for it may be that Allah guides him. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.