My first business partner was a good friend from high school and college roommate after college I convinced him he could build something I wanted to try, and then gave him half the company :). We worked together for ~12 years and then went our separate ways after a few companies together. It didn't end well but that is a separate story.

New business partner, I found on HN, hired him for some freelance work for 6 months, then pitched him on an idea and now working on it together :).