Shadow Welsh Secretary Owen Smith has been explaining why he and most Labour MPs are voting for same-sex marriage proposals.
Our Political Editor Adrian Masters asked him if he understands why some opponents are strongly opposed to what they see as "redefining marriage."
Welsh MPs have voted on proposals to make same-sex marriage legal. Here's a breakdown of how each one voted.
All Welsh Conservative MPs and at least one Welsh Labour MP are thought to be likely to vote against same-sex marriage plans