I believe this will help you.
1. Make a switch called 'party members' (or whatever you want to call it)
2. Make 4 events named 'partymember1', 'partymember2', 'partymember3', and 'partymember4'
3. This is a bit difficult to explain but I'll try my best. Each of the 4 events you made should have the condition to only be on if switch 'party members' is on & if actor 'example' is in party. Pay attention to this part because it's difficult explain; in each of the four events make a page for each of your possible party members. The system reads these from right to left so make sure to set them correctly. For example: [Event 1 page 1: if actor 'actor1' is in party. Event 1 page 2: if actor 'actor2' is in party. Event 2 page 1: if actor 'actor2' is in party. Event 2 page 2: if actor 'actor1' is in party] This way those two events won't show the same characters. If this part isn't clear enough let me know and I'll attempt to explain it better.
4. At the start of your scene fade-out the screen.
5. Use the event command 'Set event location' to set those 4 events to the players location.
6. fade-in the screen
7. Make four move routes; one for each event. Event1 [Through on, move left, move left, turn up] Event2 [Through on, move left, turn up] Event 3 [Through on, move right, move right, turn up] Event 4 [Through on, move right, turn up]
That should be what you're looking for. I wasn't looking at the editor when I wrote this so it may not be perfect, but if you mess with it a bit it should work.