May I share sync serves with my family ?

Hello
May I share sync serves with my family ?
My family can use different vault in obsidian with password.
Or it is not allowed?

I don’t think it’s forbidden, but there’s no way to setup separate accounts under a single subscription, so everyone you shared it with could access every synced vault and the account settings.

Sync has a vault-sharing feature now, but it requires each person to have their own subscription.

Or, you can use services other than Obsidian Sync. Here’s a starting point: Sync your notes across devices - Obsidian Help (see also the Remotely Save plugin).