GPG

$ gpg --edit-key <key-id>
gpg> adduid
Real Name: <name>
Email address: <email>
Comment: <comment or Return to none>
Change (N)ame, (C)omment, (E)mail or (O)kay/(Q)uit? O
Enter passphrase: <password>
gpg> uid <uid>
gpg> trust
Your decision? 5
Do you really want to set this key to ultimate trust? (y/N) y
gpg> save
$ gpg --send-keys <key-id>

Ref:

https://superuser.com/questions/293184/one-gnupg-pgp-key-pair-two-emails