After further research through the forums, it would seem that according to this thread: http://www.twcenter.net/forums/showt...rals-age-limit, the age of death for Family Members is hardcoded and can not be altered. I was looking back again over this thread, and caught two more interesting posts that might shed some light on this issue:
Another example of this issue showing it's commonality amongst the players, seen in post #106:
On the flip side I found statement on post #133:
Now, he could be just talking about turning the Roman Leadership System on and off in this quote, but he is actually talking about any changes in general, then there is no way to fix this without starting a new campaign. So, maybe in the future Muizer, (who I think is the main developer of the RLS system?), will be able to shed some light on this topic, but outside of that I see no way in which this bug can be fixed.