This is where vesting schedules are everyone's friend. I generally think that you should get a grant for the same number of shares that the three founders do,

This is where vesting schedules are everyone's friend. I generally think that you should get a grant for the same number of shares that the three founders do, but if everyone's on a vesting schedule, they'll still own more than you for the next four years from today. After that, you'll all be on the same economics. Here's the idea: let's say the three of them founded the company 9 months ago and they all have 100 shares each. You should get 100 shares as well, but let's put everyone on a vesting schedule that says you get 2.08% of your shares vested for every month served. So the three founders should get credit for nine months of service and 18.75% of their shares should immediately vest (as of the day you join) while you're at 0% vested. At month 48 after the company was founded, the three founders are fully vested while you're 81.25% vested. At month 48 after you joined the company, you're 100% vested and are on the same economics as the three founders.