Research suggests those in happy long term relationships live longer. Makes sense. Chess performance who knows? Perhaps if newly wed Aronian storms the candidates (having flunked it previously) and snatches the WC from Carlsen we can draw conclusions. Although Carlsen has a new lass as you say so anything could happen.
Do men with girlfriends/wives play better chess?

I think it a chess player has a supporting girlfriend or boyfriend they will tend to do well but if that chess player unfortunately gets a bad girl/boyfriend then his/her performance will be bad. consider Wesley so when he had all those family problems he didn't do so good at that stuff Louis tournament in 2000 idk (I forget the year) but as soon as that was cleared up and he entered good hands he won the 2017 St Louis tournament.

If they are not supportive then it may make them worse I would guess, bc every time they want to play or study chess their girl will roll her eyes at them discouraging chess study and play.. hehe
a guy called west guy.. he lost to 1800s after getting married. relationships are fine but chess players should marry only after retiring..

Just did a quick calculation on the members of my club (not counting kids who would distort the results)
Average married Elo = 1654
Average unmarried Elo = 1686

I think it a chess player has a supporting girlfriend or boyfriend they will tend to do well but if that chess player unfortunately gets a bad girl/boyfriend then his/her performance will be bad.
This makes sense. Family/friend issues can affect your whole life, not just your hobbies. I am aware, however, that there are obviously many other factors that can affect your quality of play.
Whenever Carlsen does badly the media sometimes blames his girlfriend, even when it is obvious that there could be many other reasons for it.
https://www.ichess.net/2017/07/29/magnus-rating-drop-new-girlfriend-reason/
This might be a controversial topic, but it's something that I'm interested in.
I've heard some people say that having a relationship can potentially distract you from your career, especially when it comes to something as mentally draining as chess. However, Carlsen seems to be doing just fine with his girlfriend. After all, he recently won the 2017 Isle of Man Open! And surely a woman would want a man that is successful, no matter what job he chooses to do?
Feel free to share your thoughts on this subject.