When we sent our Save-the-Dates one of FI's friends was casually dating a couple different gals and so we did not invite with a +1 (space limited, etc). Fast forward 3 mos and he and one of these girls are now living together. Based on what I've read on the e-board so far, I think we need to extend a plus one to his SO. Is this correct? I'm a little concerned because it will take us above our limit...