We had a husband and wife working in our department and it seemed to work out just fine for several years. Then the husband got laid off. Awwwkkward.
We had a similar situation years ago that really was bad. The wife was exec assistant to a VP, the husband was in a different group in a worker bee position. There was a modest layoff and the husband was one of the people who got it.
The wife was in a position to make life miserable for her husband's manager, that manager's director, and that director's VP (let's call them the gang of 3), and she did. And within 2 years, the manager and the director were gone.
There were very subtle things that you couldn't do anything about. If one of the gang of 3 wanted to meet with her boss, there was no available time. Emailed reports and phone messages from them would occasionally not reach her boss somehow. Her boss found many things to complain about in the gang of 3's handling of just about everything because she would find ways to make her boss aware of things without making it seem like she was being vindictive.
The most outrageous IMHO was when the director wanted to meet with her boss on an urgent matter and she told the director to come by the next day at 1 PM knowing the director had a doctor's appointment at the same time. The director asked her to find any other time to meet because he did not want to reschedule his doctor visit. She said she would take care of it then did nothing. The director goes to the doctor, and at the appointed time the VP thinks the director is a no-show for the "urgent" meeting and asks her to locate the director. She says she can't locate him and then tells the VP, "I'm sorry I didn't call (director) to remind him of the meeting. I was really busy and I usually call to remind him when he has a meeting with you. I guess it wasn't that urgent after all."
So that planted the notion with the VP that (director) is a scatterbrained person who can't keep track of appointments that HE asked for and said was urgent.
Even though she and her husband were in different departments, it was an ugly situation.