Yes, but will the church tell them that what they are doing is sin? Or will it give them communion and accept them as brethren?
Yes. The Catholic church is very clear on sins. The Catholic Catechism provides the teachings of the Church.
Why are you so concerned to judge the sins of others or the actions of others in the Catholic Church? Are your sins public and subject to scrutiny? Should we not follow Jesus teachings of Loving God and our neighbor as our self?