I remember in my games that I've played in that the original Flavius Julius lived an average of eighty years. Although I did have one Scipio lived to his nineties but all he had were daughters and not even one son but he did adopt 3 fine young men (one of them was already a 4 star general). The old geezers can have kids at that age as long as your daughters (their wives) are still young enough to have kids (I figure around 35 is the beginning of the barren years although there are exceptions). So if u do marry them off to an old guy, make sure the daughter is still in her twenties, stick him in a city and hope for the best.