A tidbit from John Calvins Commentary on romans 5:(unedited)
14. Even over them, etc. Though this passage is commonly understood of infants, who being guilty of no actual sin, die through original sin, I yet prefer to regard it as referring to all those who sinned without the law; for this verse is to be connected with the preceding clause, which says, that those who were without the law did not impute sin to themselves. Hence they sinned not after the similitude of Adam’s transgression; for they had not, like him, the will of God made known to them by a certain oracle: for the Lord had forbidden Adam to touch the fruit of the tree of the knowledge of good and evil; but to them he had given no command besides the testimony of conscience. The Apostle then intended to imply, that it did not happen through the difference between Adam and his posterity that they were exempt from condemnation. Infants are at the same time included in their number.

From the pen of Jim_M
The bible teaches that the children are punished for the sins of their fathers, to the third & fourth generation, if they are guilty of the same sins, Exodus 20:5 (of those who hate me) and if they do not repent, Numbers 14:18 (forgiving sin and rebellion).This is made very clear in Ezekiel 18, when the Jews accuse God of “sour grapes”. Consequently no one is a sinner just because Adam was a sinner, we all become sinners the same way Adam became a sinner, by sinning and not repenting.