No, actual sin is not possible before the age of reason. If a child commits an act that would be sinful coming from a mature mind, then it might be a sin of the parent, but never of the child. All the Commandments are to be obeyed by all, but if a child breaks a commandment, he is not sinning. The parent has an obligation to rear the children properly of course, and failure to do so is a sin on the parent.
There is no legalistic definition of the age of reason. When a child shows an ability to act like a moral agent, the parent is advised to confirm the child in the faith and introduce him to sacramental life, including confessions. It is a gradual process. It is generally thought that the age of reason arrives between 7 and 14, depending on the child and the circumstance of upbringing. Even in an adult, the mechanism of invincible ignorance continues to operate in one who is prevented by circumstance to learn the full extent of the Divine Law. It is assumed though that one past the age of reason is at least vincible as regards the Natural Law, such as the Ten Commandments.
I love invincible ignorance
You losing it rapidly...
That's interesting, I didn't know that was the Catholic position. We're probably not really too far apart on this, as I don't think small children are held accountable either. As you may very well also, I just know from personal experience that they are capable of making decisions, even to the point of repeating them over and over when they know darn well better. :)
FK: I love invincible ignorance.
You're losing it rapidly...
BWAHAHAHAHA! But when it comes to new and different ways of being ignorant, you'll find that I am a rather resourceful fellow. Just ask my wife. :)