What is the ruling on commingled funds that originated from dubious sources (bribes and unlawful commissions) and then grew through legitimate projects, and what is the ruling on marrying into families who possess such wealth? Is it religiously preferable to avoid relationships with them as a path to piety, scrupulousness, and avoiding dubious matters?

If the suitor has no connection to the family's illicit money and his income is lawful, then there is no objection to accepting him if he is of good character and religious commitment. However, if his income is from the family's money: if all of his money is illicit, then it is not permissible to accept him. If most of his money is illicit, then it is permissible to accept him, though disliked. The most likely scenario is that this family's money is mixed, and the fruit and growth of illicit money depend on the effort of its owner. Therefore, there is no impediment to accepting him as a husband, while advising him to dispose of the illicit principal.