How should I deal with my non-practicing family, especially regarding their financial requests which are doubtful in legitimacy or might be used for something unlawful?

A Muslim must strive to elevate his family through righteousness, continuous advice, reminding them, encouraging them, and warning them. He should explain to them the insignificance of this world and its fleeting nature, and that blessings are in the hands of Allah, who disposes of them as He wills. The caller to Islam should use effective means to invite his family to goodness and be a good role model. As for interactions, the guiding principle is Allah's saying: "And cooperate in righteousness and piety, but do not cooperate in sin and aggression," and the Prophet (peace be upon him) said: "There is no obedience to one who does not obey Allah." Therefore, it is not permissible to assist in falsehood.