Upvote:5
The Christian answer to this is simple and ancient. God is eternal and has always existed. He does not have a creator. He is the 'first cause', or 'uncaused cause'. Speculation about how that came to be (bearing in mind that 'came to be' is a phrase implying time and causation, which may not be appropriate) are just speculation on the part of individual Christians.
It should be said that a small minority of sects, notabley the Latter-Day Saints, don't agree with the above statement.