I don't really care whom he considers a brother or sister of whom he is not by blood a sibling. What I care about is whether this is a declaration that he will treat some people with prejudice and others deferentially based upon their religious beliefs. If the answer is yes, then he openly violates the U.S. Constitution which, given the First and Fourteenth Amendments together, prohibits an elected officer from making those distinctions.
If he is merely making it known that, when not serving in an official governmental capacity, he hopes to persuade people to accept his beliefs, but otherwise, especially when officiating as Governor, does NOT make distinctions between his constituents based upon religion, then he should be safe.
Even Evangelical Christians have the right to run and be elected to office.
This is just a case of "wait and see."