All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger.
If your husband and his brother gave this money to their father as a gift or donation without expecting him to pay it back, then they are not entitled to any share of the house and they have no right to ask their father to repay them this money. And if they gave him this money as a loan, then they are entitled to ask for what they gave him. If they gave him this money in return for being partners in the ownership of the house, then they are entitled to a share of the house that is proportional to the money which they have paid.
If the two parties disputed about the nature of the payment and whether it was a gift or a loan, you should refer the dispute to the Shariah courts. However, our advice is that the sons try to reach an understanding with their father and be keen on pleasing him, even by giving up part of their rights. Indeed, dutifulness towards the father is one of the dearest deeds to Allah and one of the means to win Paradise. Abu Ad-Dardaa', may Allah be pleased with him, narrated that the Prophet, sallallahu ‘alayhi wa sallam, said, "The father is the middle door of Paradise, so it is up to you whether to lose that door or to guard it." [Ibn Maajah and At-Tirmithi]
Allah knows best.