What should I do about proposing to a girl if there are suspicions about some members of her family being involved in illegal trade, while it is difficult to ascertain her father's involvement?

If a girl is religious and of good character, Islamic law encourages marrying her, for the Prophet, peace and blessings be upon him, said: "So win the one who is religious, and you will prosper." The mere engagement of some of her family members in unlawful matters does not preclude marrying her, for Allah Almighty says: "And every soul earns not [anything] except for itself, and no bearer of burdens will bear the burden of another." As for one whose engagement in unlawful matters has not been proven, the default is his innocence, and it is not permissible to harbor ill suspicions about him, for Allah Almighty says: "O you who have believed, avoid much [negative] assumption. Indeed, some assumption is sin."