You mess around with Robin

Robin sneaks touches of your cock through your shorts every chance she gets. It's tough because your father can look back at your seat easily. He's inattentive to the family, and especially his wife, but he's very attentive to the road. Soon in the drive he says he needs to stop for gas and you get an idea.

When you stop, you say you need to get out and stretch, and wink at Robin. She follows your lead and gets out too. After feigning some stretching, you climb back in but this time you get back in behind your dad and have Robin behind your mom. Your mom may catch you, but she won't say anything with your plug in her ass.

Robin is curious what you have planned, but catches on when you pull a pillow out and put it on your lap. She fakes a yawn and lays across the back seat to put her head in your lap. Your mom watches and is visibly jealous that Robin's right up against your cock but appears to distract herself turning back to her phone.

You feel Robin's hand slide under the pillow and start unzipping your shorts to get your cock out. She starts stroking you, under the pillow at first. You start to get lost in the pleasure of the moment when you notice a new text light up your screen.

'if that was my head right there, I'd have you in my mouth right now'

You get a naughty idea and text back. 'You mean like this?' you grab Robin's head and move the pillow so your cock is free. You position her with your head at her lips and let her start licking and gently taking your cock in her mouth. You look up to see your mom getting wild with jealousy. She's probably shifting in her seat to feel the butt plug move in her.

"Mom, you look tired, why don't you take this blanket," you say as you pass her a billowy blanket from the back. She covers herself from her neck down. You go back to focusing on your sister working on your cock when the next text comes.

Your plan worked, and you can see under the blanket your mom is touching herself because she sent you a pic of her pussy, fingers glistening from her wetness and spreading herself for you. 'you enjoy her now, but remember that I'm the one who can deep throat that monster when she can't.' you wish you could remember, but will have to make sure you find out later.

You feel yourself getting close and at the perfect time comes another picture from under the blanket, this time her naked breasts. 'and don't forget how much you love to play with my bigger tits.' it all pushes you over the edge and your mom watches from the front as you unload in your sister's mouth and she sucks you like a straw.

You recover and text back 'hope you enjoyed the show as much as I did... We'll have to make our own later."