Living together in itself is not a sin, but cohabitation (living together while having premarital sex) is objected to by the Catholic Church because it disposes all couples who do live together before marriage to mortal sin (partaking in sex outside of marriage), which in turn can be detrimental to our spiritual lives ...

Why is cohabitation a sin?

The Church's teaching on cohabitation is not an “arbitrary” rule. Living together before marriage is a sin because it violates God's commandments and the law of the Church. St. ... It is a decision to turn away from sin and to follow Christ and His teaching.

Is live in relationship a sin?

Live-in relationship is neither a crime nor a sin, the Supreme Court has held while asking Parliament to frame law for protection of women in such relationship and children born out of it.