Normally you need to establish a relationship to have a successful scene. There are times when a scene works fine without one, but usually it's a good thing to have.
You can use the tried and true "Husband/Wife", "Mother/Daughter", "Doctor/Patient", etc. But it's always more fun to create a very specific relationship. When you get a chance try and think of some cool ones. Pay attention during the day, you'll see some good ones.
Here are a few that I've come up with.
- Rival Doctors
- Roommate/Other Roommates Girlfriend
- Commissioner Gordon/Batman
- Pilot/Ground Control
- Two Pregnant Women
- Author/Imaginary Main Character of Authors Book
- Two Horses in a field