I have wanted Xavier since I was 15! I always had Xavier Loki (pronounced Low-ki) in mind.... I have since grown up a bit a have a few other middle names in mind....

Xavier William
Xavier Jude
Xavier Locky
Xavier Khy

as for the others....
Oliver Keinan
Oliver Chase
Oliver Beau
Oliver Dean

Zachary James
Zachary Ethan
Zachary Davis
Zachary Levi

Good luck with it all! Having DH and you agree on a name is the hardest part of pg I think! lol