I didn't read the replies but I can tell you this (be advised that as a Christian, I speak solely from the view of Christianity):
The bible says that all have sinned a fallen short of the glory of God. The fact that you have recognized and shown remorse for your sin is the first step in cleansing yourself.
If you feel convicted strongly to speak to your family about this, then that is the spirit of the Lord telling you that you need to get this out in the open.
However, if you have confessed your sin to the Lord and then completely turned away from it leaving it in the hands of God--God finds no fault in this and you and He will be okay. Isn't that the most important thing, that our relationship with God keeps us in perfect peace with Him?
God's desire is that we are led by what we feel He is saying to us. Only you can know for sure if you should follow one path or the other.
If you feel, that you have gotten cancer because of your past actions, than the verse "whatsoever a man soweth, that shall he also reap" has already come to fruition. It seems as though judgment has already given from Heaven, would you really think that God requires you to inflict pain on your family with what seems to be the "real truth?" Please be careful that sometimes this is a trick of the devil to cause disharmony in an already weakened and sad environment (your family) to pull others in your family further down.
You've confessed to God and on this board. Christ never told sinners after he healed them to go and apologize to everyone that they've hurt to "seal the healing." He always said, especially to the woman caught in adultery, "I don't condemn you, now go and sin no more."
I pray that you find peace during your final days.