If a believer never sins, does he still need to repent for his parents and grandparents (on back) misdeeds or sins?
Carlita, there is no such person as believer who does not sin. If you understand what sin is, you can understand why this statement is true.
The sin that Jesus came to give his life for is the imperfection in our soul, our imperfect flesh that has a propensity now to want to go the wrong way. This was inherited from Adam. (Rom 5:12) This is sin that we cannot control. No descendant of Adam is born without it.
Paul described a inner struggle with this "sin" at Rom 7:14-25:
"For we know that the Law is spiritual, but I am fleshly, sold under sin. 15 For I do not understand what I am doing. For I do not practice what I wish, but I do what I hate. 16 However, if I do what I do not wish, I agree that the Law is fine. 17 But now I am no longer the one doing it, but it is the sin that resides in me. 18 For I know that in me, that is, in my flesh, there dwells nothing good; for I have the desire to do what is fine but not the ability to carry it out. 19 For I do not do the good that I wish, but the bad that I do not wish is what I practice. 20 If, then, I do what I do not wish, I am no longer the one carrying it out, but it is the sin dwelling in me.
21 I find, then, this law in my case: When I wish to do what is right, what is bad is present with me. 22 I really delight in the law of God according to the man I am within, 23 but I see in my body another law warring against the law of my mind and leading me captive to sin’s law that is in my body. 24 Miserable man that I am! Who will rescue me from the body undergoing this death? 25 Thanks to God through Jesus Christ our Lord! So, then, with my mind I myself am a slave to God’s law, but with my flesh to sin’s law."
I have never seen it described better. But you see we have a rescuer?
The sin that we "choose" to commit is the one we CAN control. We are in the driver's seat...we are the captain of our own vessel....we steer it where we want it to go. If we deliberately crash it into a large object, can we complain about the damage or the cost to repair it?
We all stand or fall by what we choose to believe, so if we inherit beliefs from our parents and grandparents, without substantiating them, we are like those people who for generations teach false truths to their children. Is it the children's fault that they are taught the wrong things? No, but if they hang onto those false beliefs and perpetuate them without questioning them, then they are as culpable as their forebears. The truth is not hidden...it is out there for all to see, examine and choose....or reject.