Not really. chown userone:usertwo /directory would make the directory owned by userone but in usertwo's primary group. This would enable userone to access it as owner and usertwo (and anyone else in group usertwo) to access as group. You would still have to ensure the usertwo group had at least enter permission for the directory and every directory above, and probably read and write permissions for the directory as well. If the directories above are not grouped to usertwo they would need their world (others) permissions set. Enter permission (--x or 1) means you can access the directory's contents. Read permission (r-- or 4) means you can list its contents and write permission (-w- or 2) means you can create or delete files.
Your problem is most likely a 700 (drwx------) permission in a directory above. This prevents group and others accessing any directory below and is the default (and only strictly safe) permission for a user's home directory. That's why you should put the shared directory outside a user's home.
Whilst, for maximum protection against interaction, it might be wise to use LXDE and KDE as separate users, they do store their configuration in different places, apart from non-specific things you would probably want the same in both environments so, unless you want your LXDE set up differently from your KDE at a user rather than desktop level, there should be no harm in accessing them from the same user. I have both on my system and I use KDE for local access and LXDE for remote access as the same user. That's because KDE reacts badly if it's opened at a different screen resolution from usual and my laptop has a smaller screen than my desktop, so I use LXDE instead for remote access so KDE is not disturbed. That's my reason for using both desktops. What's yours? If we knew that we could probably hazard a guess as to whether you really need different users.
I had a menu crash in KDE after making some configuration changes in LXDE (wallpaper, icons, etc.) I didn't change resolution. It was suggested up here n the forums that I perhaps use separate user accounts for KDE and LXDE.
I now understand why a shared directory should be set up. Wow! Linux really is secure!:)
The reason I'm jumping into LXDE is because it's lightweight and faster than KDE on the system I'm using. It's a spare box I've set up and only ha 2 gigs or RAM. I'm editing my cartoon features in Gimp and Scribus so need the extra resources LXDE would have. This is due to not having access to my main computer box. Once I have that back n place, then no problems. I'm also considering buying/building a new box. My nephew (an IT wiz) would do the actual build for me.
Until then, I'm using the spare box. And due to your reassuarance and the input of others, I'll mark this solved and simply run KDE and LXDE under th same user.