However, despite your definition according to St. Thomas Aquantis, it cannot be correctly applied to a child.
You are a child living in your parent’s home and so is your brother. If you are not yet 18, you are still in formation to learn these things.
A child does not naturally know that he must behave in a certain way. Tweens and teens must go through a process of disobedience to learn where the social boundaries are.
How old is your brother? I’m guessing not much more than 14 or 15. Probably younger. Expecting a child to act like an adult at all times is wrong. Your brother reached out to you for help. As an elder sibling, you were downright abusive. Being kind would have cost you nothing and would have modeled much better behavior for him to copy. Instead, you modeled crass beligerance and perhaps a good deal of your own “efemininity” if we’re going by St. Thomas’ example.
If you are all grown and in your 20’s…then there is a reason for concern–but what you are doing now is simply berating a child.
Given that you are also a child, your impatience for another child’s actions is understandable…but that does not mean that you can apply vice to his actions. He’s a child.
Also, I think that you’d be wise not to name any #1 sins that affect modern men. You are not a theologian nor a psycologist or doctor of the church.