I like the basic idea, but why Birth/Rebirth? I must say, I don't quite see the difference here.

How about: Life, Death, Transition?

One to protect the living, and life force.
One to protect the dead, from being raised as undead, being called back from the afterlife against their will, and so on.
And one, a bit like Death of the Endless, who is present at birth and death and makes sure everything goes smooth.


Though I'm actually not sure why these are archons... they sound more like neutral forces to me than lawful good ones.