Listed how? On your benefits? For a flight? I'm assuming you mean on your benefits so I'll answer that. You may have your spouse, mom, dad, and children. If you don't want to list your spouse (because you don't have one) or your parents (because they don't travel) then you can choose a substitute for any of them.

The spouse, parents, & kids fly standby for free on Frontier and have the same access to ZEDs that you do. The substitutes fly standby on Frontier at a reduced rate (around $36 per segment) and you can designate 1 of them to have limited access to certain ZEDs.

I have my wife, kids, and in-laws listed on my benefits. My mother-in-law is the one I've designated for ZEDs. She flies JetBlue several times a year using that.