Ott says that every answer of the Holy Office holds the theological note of at least Sententia Communis. This means that Catholics are bound to accept them unless they have grave cause. Below is the answer of the Holy Office regarding the purpose of Matrimony. Ott also says that since this particular answer goes back to St. Thomas and before, it holds the note of at least Sententia Certa, which means that we are bound to believe it based on the conclusion of the Church. The following is taken from Denzinger. Vatican II’s teaching and subsequent papal documents simply discussed the two ends of marriage but did not make these distinctions, leading many to believe that the things denied here were in fact not denied, and adding to the general confusion of faith and morals. Nevertheless this has already been clarified since 1944. Bottom line: the primary purpose of Matrimony is children, and the secondary purpose (mutual support and regulation of lust) is subordinated to the primary purpose. These purposes are not equal in importance for Matrimony. Confusion about this point has had a massive impact on the annulment crisis.