@Max Tanenbaum excellent point about the puppy vs adult and the landlord reference. 

I suppose for any situation with more than one adult tenant, it would be a good clause to include.

They are grown adults and should abide by the law and lease.if your lease doesn't cover pets, then you should add some pet rules that could help both protect you and your tenants.

Even though I braved some of the worse parts of the city of Houston, TX as a child, I wouldn't dare househack in the same neighborhoods as an adult.

They are both living there and they're both adults put them both on the lease.

Then as was mentioned, personally speak to the adults who live there.

You may be able to put limits on the total number of humans allowed in the unit, credit scores above X for each adult, no rude people, people who smell like alcohol at 10AM, smokers, leather-wearers, vegans, etc.  

My intention was to give the apps to all adults in a household if they are interested in the property.

For me, I would never put a male roommate with 3 female roommates, where the 3 female roommates did not give their approval and do not know the guy.  

I will provide housing to Intellectually Disabled Adults in the near future.