How did Roman Catholic Church opposition affect same-sex marriage debates in Belgium and Spain?

In Belgium and Spain, the legalization of same-sex marriage occurred despite official opposition from the Roman Catholic Church, which is the predominant religious institution in both nations.1

While some countries with a single state-sponsored religion have seen their dominant faith influence the path toward marriage equality, Belgium and Spain represent cases where the cultural homogeneity associated with the Catholic Church did not result in the application of religious doctrine to the civic realm. Instead, these nations proceeded with legalization despite the church's stance, demonstrating that the influence of religious institutions on national policy can vary significantly even in countries with strong historical religious ties.1