Include third person roommate in lease?

[Shera Gregory]

We are considering renting to a couple who also have a friend they want to have live with them to help cover the rent. The couple together make exactly the 3x rent that we require. The third person makes enough to bring this up to over 5x rent. This third person had some drug problems and an eviction but seems to have been doing well for the past year. He spoke very highly of his friends, says he understands if I don't want to rent to him but asked that I not hold it against the couple. I was considering just putting the couple on the lease and letting them have the guy live with them but I think things could get sticky if for some reason they were to leave or have problems and then I have a third person living in the house with no lease. Ideas? This is in Virginia.