Sorry, no. He must join using your recruit link, or he will not be your recruit.

A player must join the game by using your recruit link for them to become your recruit, and in the same server.

If you give someone your recruit link (found in Account -> Recruits) and they sign up for the game, they become a recruit of yours. If any of your recruits upgrade their accounts (or someone else upgrades it for them), you will be given a bonus of 10%...

Players that recruit 5 or more upgraded players into the game will have a recruiting badge displayed in their profile. Only recruits that joined the game using the recruitment link and that have upgraded at least once will be accountable.