How old were Cain and Abel during their conflict?

We do not really know exactly how old Cain and Abel were when Abel was murdered by his brother.  But we do have clues to give us a close estimate.  We know that Cain was Adam and Eve’s firstborn (Genesis 4:1) and we can assume that Abel was the second born, but we don’t know exactly how far apart they were (Genesis 4:2).  We also know that Adam was 130 when Seth was born (Genesis 5:3) and that this was close to the death of Abel (Genesis 4:25).  So Cain and Abel were probably around 100 or so when this event occurred.  So while they were young for this time period, they were not children by any means.