You have started a couple of guest linux sessions on your pc, that you do not need anymore (ie giving access to your children while on holiday 🙂 ), and you want to close them from your own session.
Find out about the guest users by using who:
who ... guest-kk9tnS :2 2015-08-09 17:39 (:2) guest-kk9tnS pts/21 2015-08-09 17:40 (:2)
and then kill the sessions using pkill:
sudo pkill -9 -u guest-kk9tnS