Attach multiple times to a single screen session

screen -x is the option you want (coupled with whichever other options you desire).

The -x replaces -R in this case.

Try

screen -aAxR -S x

-x is the option that does what you want.

I'm personally a fan of:

$ screen -rxU

-r resumes a detached screen session -x resumes a not-detached screen session -U tells the terminal to use UTF-8 encoding (which I use exclusively)