Usage of login plugins (like nLogin, etc.) on online server

I have players whose siblings often log into their Minecraft accounts and join my server, causing issues that the original account owner later has to report in a ticket to fix. Should I consider adding a second login screen (like nlogin or something similar) when connecting to my server? It would be similar to AuthMe but with online-mode=true, just to enhance security.

Is this likely going to drive away legitimate players, because they might think that the server is cracked if they see a login screen when joining. I'm kind of in a dilemma here.