Q: Trying to use Family Sharing, emails do not work

Just heard about Family Sharing and I feel this would work well in our family as my kids are 12, 10 and 5.

They do have email addresses set up already, but when I tried to set up Family Sharing,it says I cannot send an invitation your your own account.  Why would both of them be on my account? At one pint did I add them? How would I get them off so we can change to family sharing?

(FYI- my daughter will be 13 soon, so not sure if better way once they are 13?)  I tried to make their own Apple ID with my birthdate and CC info, but it also said the email addresses were invalid?

I'm confused?

Thanks