I love the spelling
Cristian, and the pronunciation (more like kree-STyAHN). It does seem strange to leave the H out of
Christian and leave it in
Nicholas. I would only expect to see
Cristian used by Spanish-speaking parents. I do prefer the flow of
Nicholas Cristian, but
Cristian Nicolas has a lovely flow (the Spanish pronunciation emphasizes the last syllable of each name).
I think
Layla Nikita,
Cruz Tyson, and
Cristian Nicholas go very well together, as far as style goes, but I don't like
Cruz and
Cristian as brothers, because they both have meanings related to the cross.