Let me see if I got this right. You're at a party enjoying yourself when two girls you don't know from a hole in the wall, come up to you and demand you drive them back home to their dad. So, if you don't drive them home, you're holding them against their will? Huh? Double huh?
Dude.
Grow up.
Someone brought them to the party. You are assuming that they didn't ask the person who brought them. When you cart 17 yo girls around you are repsonsible for them. When they want to go home, you take them or you are holding them against their will. If I was at that party and they asked me I would have.
Did they demand? Maybe. Did they ask. More likely. I guess it's more important to sit around and get drunk at a frat party then to take responsibility, when asked, to bring young women home.
You left out the part where their dad shows up and you and your friends surround him to prevent him from taking the girls home when they are requesting to go with him.
Yes, you are holding them against their will if, in fact, you let them into the house!