I had the same thing happen. My business partner and I left our jobs simultaneously to go all-in as CEO/CTO, pre-funding. We jointly agreed we were "co-founders

I had the same thing happen. My business partner and I left our jobs simultaneously to go all-in as CEO/CTO, pre-funding. We jointly agreed we were "co-founders", exchanged in writing what I believed was a fair cap table, agreed in writing I held the most shares of anyone, and we each agreed to take only $30K/year after funding. But we made the huge mistake of delegating legal solely to my co-founder. He secretly created a small equity pool for his "co-founders", and he secretly made it so the negotiated percentages we thought were fair only applied to the "pool" and not the whole company. Nine months in, I discovered I was vesting ~0.3% per year. He took nearly all the equity for himself. Despite our agreement to be "co-founders", he suddenly told me he didn't know what the word meant at the time, and that actually he was the sole founder. When I left due to this, my business partner told new investors there was never a CTO, then demanded in writing that I remove CTO from my website. This is despite him routinely putting in writing that I was CTO -- not to mention that I was responsible for all of our products, coding them largely myself.