[forgot-my-pw]

Actually, they have discounted rate for additional users:

Does Google Fi offer plans for groups or families?

Yes. If you’re new to Google Fi, you can set up a group plan during your checkout process. Just have the intended plan owner click “Join Fi” to get started.

Just like an individual plan, each month you’ll pay $20 for unlimited talk and text, then add $15 for each additional person. Data costs the same at $10 for each GB used.

If you’re already a part of Google Fi you can invite people to your plan here. You can have up to six people, including the group owner, in a group.