Is This A Novel In A Series?

Captive In The Berghof was originally book 3 in a 4 book series. First of all we had King Abdullah’s Tomb, which was originally entitled Those Who Dream By Day. Book two was called In the Shadow Of The Sphinx. Berghof was book 3. And Hitler’s Trinity was book four. The first two novels, King Abduallah’s Tomb and Sphinx, have been orphaned and cut off from the main story by later revisions, though they seem to be about the same Dora and Edward. My son calls it an alternate time line. The only two novels that fit together are Berghof and Hitler’s Trinity, which are one and two in a series.