It's not quite random, although there is a bit of that in the heir-producing system for STW. Heirs are reflected by the actual history of the real, historical daimyos; for example, the STW Oda Nobunaga comes of age right about the time the real Nobunaga did, etc. It varies with each clan; Hojo has heirs like crazy while Shimazu hardly any at all.
Now to the random part: While births and early come-of-age heirdom can be predicted, just where these sons enter the game more chancy. Until an heir assumes the throne (and gets the heavy cav bodyguard), he is assigned to a banner as it's leader and can easily be killed without you knowing it. You then might suddenly find yourself without heirs while you were expecting to inherit. In another vein, the exact death of your original daimyo is less fixed and some can last for years longer than thereal-life counterpart did.


[This message has been edited by solypsist (edited 09-03-2001).]