this seems similar to games with "alignment" (good~law, neutral~neutral, or evil~chaos) game paths.
as they too merge at choke points where your "alignment" (ie event choices made) affect the situation of that choke point for you.
(forgive my text drawing visual picture's lack of ability, lol)
.......______ good _____
....../.......................\
start-------- neutral ------- choke point 1
.....\______ evil _______/
as obviously... you don't want a masssive branching tree... lol. You must have (re-)merging of the branches!
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here's an example of it in action in a game (Ogre Battle Series: Tactics Ogre for PS1):
http://luct.tacticsogre.com/valeria.htmlhome page of the site:
http://luct.tacticsogre.com/(Final Fantasy Tactics is NOTHING compared to the Ogre Battle Series, hehe)
you can see how it branches and then re-merges at choke points