need to sign agreement with sublease tenant

[Tony W.]

I have a 5/3 house I am about to rent out to three people.  They intend to rent out the remaining two bedrooms to their friends.  I will sign a lease agreement with the three primary tenants.  Should I stipulate in the contract that I also need to sign agreements with the sub-tenants or should I leave that to be the problem of the tenants?  I do have a provision in the contract that I get to vet the potential subtenants and have right of refusal on them.