Through he's portrayed as an instrument of God, Owen Meany causes the death of John's mother. What other deaths was Owen indirectly involved with? Do you find Owen's close relationship with death to support or undermine his miraculous purpose in A Prayer for Owen Meany?
Whether he was directly involved or not is a question likely without an answer, but Owen was there shortly before Tabitha died and felt that he had interrupted the angel of death on that task, so he at least felt he was involved with her death.
If you look at his relationship, the way that he continues to feel he sees or communicates with death, dreams of the way he will die, inscribes his own gravestone, etc., it may serve to support his underlying miraculous purpose. He also tries to make sure that other people do not die, including John by making sure that he does not have to go to Vietnam.