"Every human father begets a son or daughter with his sin nature. We may not understand completely how this works, but this is the way of the world after the Fall. Sinners beget sinners (Psalm 51:5). Always. So if Joseph was the real father of Jesus, or Mary had been sleeping around with Larry, Jesus is not spotless, innocent, and not perfectly holy. And as a result, we have no mediator, no imputation of Christ's righteousness (because He has no righteousness to impute to us), and no salvation." ~ Kevin DeYoung, The Good News We Almost Forgot.
But He is everything Scripture says He is, and He has opened up the way to save forever, completely, and to the uttermost those who draw near to God through Him (Heb 7:25).
He is the One Mediator between God and man, CHRIST JESUS! (1 Timothy 2:5).