My wife says that since her and I cohabitated and had coitus prior to marriage (we didnt come home to the Catholic church until two years into our marriage) we have no right to tell others not to do it.
The sister in-law is also Catholic, and she has a degree in Catholic apologetics/theology from a local Catholic University. The new boyfriend is a Protestant of some sort.
Considering that all involved parties are Catholic / Christian I was truly not expecting the backlash.
you have every right to tell others not to do it, inside or outside your house, it’s called admonishing sinners, and all Catholics are called to do it, although with charity and gentleness, and it is not disrespectful or judgmental at all, the command to love our neighbor as Christ loved us means admonish and set a good example for them and to even put their lives before our own, the love of Christ to us was chiefly directed to the salvation of our souls, all he did and said, and suffered, was intended principally for that end, and we should strive to have the same love for our neighbor, and as Christ loved us to that degree, as to lay down his life for the good of our souls, then, as we are told “we ought to lay down our lives for the brethren;” (1 John 3: 16).
namely, when the good of their souls require it.
and if we ought to lay down our lives for the good of our neighbor’s soul, then how much more are we to admonish and correct them, in charity, when we see them in danger of hurting their soul(or risking the souls of others).
but as for what your wife said, someone who is not repentant of a sin really has no right to tell someone else not to do it, but you and your wife have left your old lives and entered into a new one within the Catholic church, so although you did not repent from those sins before marriage, it makes no difference, you have repented in your hearts and minds, that is what makes the difference,
but even someone who is trying to overcome a sin has the right and duty to admonish others of it, it would make no sense if we could never speak to someone of a sin we commit, since we are all sinners to one degree or another, we all have a degree or type of pride, but if we could not speak on it because we commit it, then sin would never be spoken of!
but that is referring to those who are trying to overcome their sins, not those who willingly and purposely commit them without shame…
and you also, as you said, have children to guide and to guard, it is yours and your wife’s duty to protect the morals of your children, and to allow your sister in-law and her boyfriend to enter your house and sleep in the same room together, would have been scandalous to your children, and likely have a bad influence on them, which the responsibility of would fall on you and your wife…it really doesn’t matter what kind of life you and your wife lived, what matters is right now you know Christs teachings and you must pass those teachings onto your children, you have to learn from your own mistakes, your children can learn from theirs, but there’s no sense in letting them experience what you did, your past is there to learn from, not to be sympathetic towards others for…we learn from our sins to become better and overcome them, *not *to be more accepting of them.
as a husband, you also have the duty to admonish your wife(the same duty she has to you), in charity, of her erroneous ideas with all this,
but be patient, as i said, with gentleness, you won’t get through to her by trying to push her along to quickly…it may even be a good idea for you both to speak with a priest together every so often.
but if you need to brush up on why co-habitation is wrong before you speak with your wife on it, here are some things that may help -
gaiaonline.com/guilds/viewtopic.php?t=17452629
audiosancto.org/sermon/20060806-Occasions-of-Sin-and-Company-Keeping.html
audiosancto.org/categories/marriage-and-family.php
hope this helps, take care