This might be a silly question buts say you started a company as a startup over a year ago and you're seeking a co-founder. You then find the co-founder which you of course have more equity over. Are you still the founder because it was your idea or are you now a co-founder?
IMHO you are founder of the company and the person who joins you later is a partner. The word founder implies that you are the one who started it. If someone started the company with you they are a cofounder. Otherwise they are business partners.
IMHO if you have more than 1 person on the founding team, no one is the founder. Everyone is is Co-Founders. That how we run it at WorkFeel.io
A founder is a person who comes up with an idea and then transforms it into a business or startup. Founders can set up a business on their own, or they can do it with others. For example, Larry Page is a founder of Google.
If a founder sets up a company with other people, they are both a founder and a co-founder. So Larry Page is not only Google’s founder, but also a co-founder with Sergey Brin. Co-founder is a term that exists to give equal credit to multiple people who start a business together.
A co-founder may be part of the vision of a startup from the get-go, or they may be brought on very early by the original founder because they have skills the founder is lacking. For example, the founder may have design skills, but no engineering skills. In that case, it greatly benefits them to bring on a technical co-founder early in the process of launching their startup.
You are definitely the founder, not the co-founder, in regards to the hypothetical given. If that person came at an earlier time when your product was in i.e. the prototype stage or your company was still an infant, he or she could have been also a founding member. He or she would be one of the first employees/hires rather than a co-founder if you are already a year in. I mean technically, you can make the new hire a "co-founder" I guess on paper if you want.