I belong to a family which practices Islam to the extent that their desires personal lives are not interrupted. My problem is that recently a pious Muslim proposed me but he doesn’t know much about my family. I have some terrible secrets regarding my parents and family which I think if he or any other person would come to know about, then he may never want to come back to me. I am confused whether to tell him or not. Sometimes (think I shouldn’t tell him because its my parents and not me. I at my best try to practice Islam in the best way possible, but at the other hand it seems to me that I would betray him if I won't tell him the real truth about my family. Please help me in the light of Qur'an and Sunnah.

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

First of all, you should be aware of the fact that being quiet while the family members are drowning in sin is not correct.  You have to enjoin good and forbid evil.  Remind them of the rulings of Shariah, the Day of Judgment and the Rights of Allah as well.  All that should be to the extent of your capability and in wise and honest manners.  The Prophet (Sallallahu Alaihi wa Sallam) said: "Whoever among you sees an evil, he must change it with his hand, if he is unable to do so, then with his tongue, and if he is unable to do so, then with his heart, and that is the weakest form of faith".  

As for informing the prospective husband the secrets of your family members, you should not do so, but you should cover them.  The Prophet (Sallallahu Alaihi wa Sallam) said: "Whoever covers his Muslim brother, Allah will cover him the Day of Judgment". [Al-Bukhari and Muslim]

Do not spare any effort to exhort your family members, probably Allah will guide them through you and you will be successful in this life and the Hereafter as well.  The Prophet (Sallallahu Alaihi wa Sallam) said: "By Allah, if one man is guided on the right path (i.e., converted to Islam) through you, it would be better for you than (a great number of) red camels". [Reported by Imam Muslim]

Allah knows best.