Complex sentence: Although many of their songs contain allusions to Christian theology and have messages (even if implied) about God, and all members of the band (past and present) are Christians, Twenty One Pilots is not considered a Christian band.
Split into simpler sentences: Although many of their songs contain allusions to Christian theology and have messages (even if implied) about God. All members of the band (past and present) are Christians although Twenty One Pilots is not considered a Christian band.