Hello, could you please tell me how old your little ones were when the…

Hello, could you please tell me how old your little ones were when they started using the kangaroo pouch? We're 3 months old, and when we hold him on our shoulders he holds his neck well, but when he lies on his tummy it's not so good, he doesn't turn over to his tummy yet, when he turns over to his tummy he immediately gets up on his forearms ?