You now have two main characters and a problem to solve within a defined space. What more do you need? Just start writing about them, drawing on your knowledge of these people. Change their names to spare embarrassment if you think it's appropriate.
Remember, you don't have to make these people exact copies of their real-life counterparts. No one's going to come and check your work and give you ticks for accuracy. Let your imagination soar. The real-life bit is just to get you started.