Type their name in the Message someone... box and start writing – you can find them by name or by a nickname, so "Uncle Jim" works too. Each message can be up to 1,000 letters, with emojis if you like. Only the two of you can see it. Your chats are kept in Messages, with an inbox, sent and seen, so you can pick up any conversation later.
Where to find it
Messages ▾ (third row of the top bar, right of Family Wall) → the box (also on the Messages page)
On a phone: if the menu is tucked away, press ☰ Menu (top left) first.
Still stuck? Talk to a real person: send us a message, or email support@mywholefamilytree.com