Hey there. My name's Demi. In case you didn't realize it, I'm the one checking your claim. I couldn't help but notice your username, Lucianvesper09. So, I'm pretty sure you're a 39 Clues fan as well. Come to chat some time? I'd absolutely love to welcome a fellow T39C fan. Oh and welcome to the wiki!
Worrying about monsters before 12 depends on the lineage or the godparent of the demigod. Normally, children of Olympian gods (Zeus, Poseidon, Apollo, etc) see signs of their "real identity" at young ages (such as seen in the case of Annabeth Chase, who had known she was a demigod since the age of seven). However, in the case of Percy Jackson, he didn't need to worry about the monsters simply because his scent was hidden through Gabe's foul stench. Now, if your charrie is a child of an Olympian, he should have seen a couple of signs showing that he was a demigod. Unless, of course, you plan on masking his scent, just like what happened to Percy.