Cannot log my husbands characters in on my pc

[Volschick]

I have my three characters logged in but cannot log my husbands characters in. I used to be able to log in his character on my machine while all three of my characters were logged as well. When I try, it says someone is already using his account. i can log his character only when I have no more than two of mine logged in. How can I do as I have before and log his three while my three are in the game?