So my friend and I were playing together and decided to marry separate people (Sam and Elliot), and suddenly we noticed many bugs. For starters, my friend joined on to my farm and married Elliot first, and saw he was unclickable sometimes. Hes stands out on the porch of my (host) farmhouse. My friend also can not embrace Elliot (kiss) at all, but I can embrace Sam. Then after I married Sam, we noticed that they would stand inside each other in the area behind the main farmhouse. (Funny to see Elliot reading while Sam is skateboarding on him. lol) I personally feel, the person that gets married to the joined friends (In this case Elliot) should stand outside the friends cabin rather on the Hosts farmhouse. Also, I don't know how you'd fix them being inside each other but its a bit odd and a big of a bug.
I've also had a problem with this... in addition to whats been stated, Non host spouses don't interact in town any more. I married Maru in my friends game and see no longer goes to the clinic on Tuesdays and Thursdays. Instead she just stands in the kitchen all day...