Adding a family member to my Office 365 account

Question

When creating a new family member account, I enter their email address and they receive a link. They click join but receive the following message, "That Microsoft account doesn't exist. Enter a different account or get a new one". I tried to accept on my end and I received the same message. I created 3 different family accounts in the past but I never received this message. Do I have to create a separate account for them first with their email and then add them to the family account?