What irked me a bit about it is that the LW's concern seemed to be only for herself/himself. Whether s/he likes it or not, these people are currently part of his or her so-called friends' lives now- however, all I heard from him or her is that the "others" don't matter to him/her, s/he doesn't want them in his or her home.
Look, I'm not an extroverted person and I tend to be cold and unsympathetic at worst and brusque at best. However, even I realize that some of my friends have significant others, children, etc.- whether or not I like them or even "approve" of these partners, kids, etc. is a moot point. Friendship isn't all about me, me, me- it's about me, you, me, you.
If the LW's concern truly is space, there are ways around it but, somehow, I get the tone that space isn't the real issue at hand. Instead, I get a cliqueish "no noobs" (ironically, even though s/he is a noob) feeling. Most people find ways to deal when their companions enter different stages of life. The LW needs to either figure out how to do things the "grown-up" way or not adjust and find other people with similar values to spend his or her time with.