How should I proceed with an underage tenant?

[Ethan Noble]

Hi BiggerPockets!

I'm going through my first real tenant screening. I say real because I didn't do a great job the first time and I'm taking my time and being diligent this time, the last people left me in a really bad spot to say the least. While there's no one to blame but myself, I'm learning and moving forward. This brings me to my current issue and I don't know where to go. I've done some searching online and a quick one on the forums but couldn't find the answer to my particular situation.

I have someone that is looking at a rental of mine. During the screening questions that I asked, I found out that they intended to have  2 adults, 25 and 21 as well as a 17 year old with a 1 year old kid. For the purposes of screening, I know that I'm going to screen both the 25 and 21 year old, but the 17 year old is throwing a wrench into things. I'm not sure how to proceed. Do I need to have the 17 year old's parents or legal guardian cosign? Do I need to run a background check on the 17 year old as well? Can I? Can someone point me in the right direction? 

As a point of note, all other factors of the 25 and 21 year olds look to be within my criteria for an acceptable tenant (prior to an actual background check). The age is just throwing a wrench into things.