To the best of my knowledge, the Church doesn't even use the word "individual," it uses the word "person" --- because "individual" implies an isolated entity, while "person" implies a social context, beginning with the family.
It's subtle, but important: you could be an "individual" in a Petri dish, but you develop as a person in a family. And the Church teaches that human beings are intrinsically social, not intrinsically isolated (individual.)
There is also an essential Chrisian role for the societies directly founded by Divine and Natural Law, namely, the Family and the Church, and for a HUGE number of intermediate institutions, and for the State (King).
Don't forget that in the days of Joseph in Genesis, God's providence ended up using the Pharaoh seizing control of all agricultural production, imposing an Emergency Preparedness Program involving the stockpiling of grain and the building of Storage Cities, and appointing Joseph to control all buying and selling during the famine.
That's an extreme situation and shouldn't be taken as typical. However, it does imply that if the emergency is truly cataclysmic, "subsidiarity" will mean a whole lot of power going to the State when necessary to prevent the extinction of nations.
In non-cataclysmic situations, though, responsibility is always supposed to devolve back to the lowest, most local, and most voluntary level that can effectively carry out the task.
How to do that is not laid out in any kind of official blueprint. It's up to us. It's called 'prudential judgment.'
Jesus calls individuals, not groups; if you want to call them persons, that’s fine, but we’re still talking about only one person at a time. It is the individual believer who accepts the gift of faith, and also the individual believer who is then responsible for his own acts and for following the Lord in his own way. It is the individual who is baptized into the Church, the individual who tells the priest that he has accepted the Faith and rejected Satan.
He then becomes part of the Body of Christ, and also part of other units (family, monastery, etc.), but it is always his unique act of faith that has brought him there. Obviously, we are all part of some institution or entity of one kind or another, and there are good ones and bad ones.
But Jesus would never have called the lame, the halt and the blind if it were all up to a person’s having developed in a healthy form. Even the most rejected, neglected and isolated individual can accept the Word of the Lord and become a Christian.
I’m not saying there aren’t better or worse situations, those that encourage or don’t encourage an individual to live a good life. But my point is that to base the argument against “gay marriage” on the statement that it’s not a healthy environment for children simply isn’t enough. If it’s all based on relative experience, you can certainly find enough people who had miserable two-parent homes and others who probably claim to have grown up quite successfully in a home where the parents may have been gay (although you’re certainly going to have a lot fewer of those).
The only argument against “gay marriage” is that it is simply not possible for human beings to redefine physical reality and declare that the law embedded in nature (both spiritual and biological) doesn’t exist because they don’t like it. The state cannot possibly go out and declare that two men can be “married” simply because the basis for the concept of marriage is actually a biological one and all the laws in the world won’t change that.
But, as I said, when some people are now announcing that a child’s biological sex is something that the child should “choose,” we see that this is absolutely a Luciferian rebellion against the Law of God which is inscribed in nature itself.
So it goes way beyond social structures.