I learned of the Concept around the age of 9-10, a mix of schoolyard and parents clarifying with "a version of the truth". Basically my mom told me: When two people love each other enough, when they hug and squeeze and kiss each other enough, the woman may become pregnant (with a younger sibling, i was familiar with pregnancy). It was enough, i understood as much as a 10-year old really can understand.
Around the ages of 12-13, school and (once again) parents went into more detail. I was disgusted enough to almost wish the previous story was the whole truth.