When I do /seen on my user its shows all my other name I updated too so if u can make this private so no one can see are last user name only are current name this would be great
As stated by CollinPotato here, username changing isn't stable with all services provided at Minetime. I think you just have to live with this, or let a administrator see what s/he can do.
Furthermore, hiding previous usernames would do absolutely nothing as players can look it up online in 5 seconds anyway.
I don't think this can be done, also people can use websites to find your previous name anyway so it doesn't make a difference.