(Tailscale employee here) For personal use, we're planning a "sharing" feature, so that you can share machines (or individual services) with friends, and they just show up on their network (after mutual approval, of course). It's a feature I very much want for my personal use of tailscale, so it's going to happen :)
(Co-founder here). If you're referring to the free tier, it only supports a single email address at the moment. What some people have been doing is to create a fake Gmail address and sharing that with their family/friends to use as a common login.
We've been exploring the idea for a free (or significantly discounted) "family" plan (or even something like that for small teams). Please stay tuned over the coming weeks for some updates to our pricing and tiers.