Wait, what? You're less than 20 people and the CTO doesn't write code? That's news, and weird in all ways. Danger ahead! But there are many things I assume in this story. Is everyone full time? How many people are there? How much of your money/time so far versus other money? Did the other founder have the same vesting schedule? Are there Angel investors? Is the CTO a friend of your co founder or other investor? There's too much unknown here. Make sure you answer all of this for your own lawyer!