Is the perpetual virginity of Mary Catholic dogma?

Is Mary’s perpetual virginity considered Catholic dogma? Is it something required for us Catholics to believe in? I do believe in Mary’s virginity, but I work with a fellow Catholic who thinks that she had relations with St. Joseph.

Yes, the perpetual virginity of Mary is a Catholic dogma. It was defined by the Lateran Synod (A. D. 649) under Pope Martin I. For more information, I suggest reading the section on Mary’s perpetual virginity in Fundamentals of Catholic Dogma by Ludwig Ott.

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