A person doesn't just automatically become converted and accept Jesus as Savior all at once. A kid growing up in a Christian household doesn't automatically mean they will follow their parents. It is always and specifically the work of the Holy Spirit in and around that person. Choosing to be open to it, recognizing the Holy Spirit's influence when it occurs, is always uniquely individual. Accepting Jesus Christ is a personal decision, not something that can be sprinkled upon a baby or absorbed through osmosis or found through good works. It is a conscious decision made by those who understand what they are doing and why.
So how did I, a kid growing up in an atheist/haphazardly spiritual home come to Christ? I mentioned the play I went to as an 11-year old, Jesus Christ Superstar, and the effect that experience had had on me. Listening to the soundtrack over and over the events of Jesus' death and resurrection stayed in my heart. I did not reject it.
Another marker on the road to salvation was God's creation itself. I'd see a sunset over the Andes, and think, this beauty was just happenstance? I'd see a pod of dolphins cavorting in our sailboat's bow wave, and think, how amazing and diverse are all earth's creatures. These just...evolved? I'd peer into the interior of a tiny shell, and notice its growth chambers orderly progression of sizing..and later learned that is called a golden section of Fibonacci numbers. I traveled the world. The world is too delicate, too complicated, too elegant to have "just happened". I saw an intelligent Creator.
Later, after I was saved, I read the following in Romans:
19 because what may be known of God is manifest in them, for God has shown it to them. 20 For since the creation of the world His invisible attributes are clearly seen, being understood by the things that are made, even His eternal power and Godhead, so that they are without excuse, 21 because, although they knew God, they did not glorify Him as God, nor were thankful, but became futile in their thoughts, and their foolish hearts were darkened.
Praise the Lord that I saw God through His creation, and thus my foolish heart was not darkened