Faith in the Bush family

How sincere are the religious beliefs in the Bush family? George W. Bush and Jeb Bush were raised Episcopalian but converted as adults to other denominations; the former to United Methodist, the latter to Roman Catholicism. My impression has been that they both converted at the request of their wives and not for political advancement. But that still leaves open the question of how sincere their religiosity is... especially in light of their party affiliation and its strict adherence to blantantly expressed Christian religiosity.