Siblings can only be displayed for members who have at least one parent connected.
Solution: Connect the member to a parent.
Open your tree and click "Invite a relative." You can either send an email invite (with an optional personal note) or generate a shareable link you can copy and paste into WhatsApp, Messenger, SMS, or wherever you'd reach them. The invite stays valid for 72 hours, and you can revoke a pending invite any time from the tree's Settings page.
Click the link in your invitation. If you're not logged in yet, you'll be asked to log in or register first — once you do, you're automatically added to that family tree as a member. Your own existing tree (if you have one) is completely untouched; joining someone else's tree never merges or overwrites your data.
Yes. You might have your own tree plus one you joined from a relative's invite. Use the tree switcher in the toolbar to pick which tree you're currently viewing or editing.
The tree owner (or an admin they've promoted) decides what each member can do — view only, or granted rights to add/edit people and to remove them — from the tree's Settings page. Separately, if two families each have their own tree, an owner can request to connect their tree to another one (e.g. through a shared marriage). Once the other tree's owner approves and turns on visibility, both trees display together as one linked view — while each side keeps managing its own tree independently.