Why not both?

You stand up to face them, and consider your options. If they're just messing with you, the best way to call their bluff is to jump to the most outrageous request you can stomach making up front and see how long it takes before they break character. If it is some kind of weird prank after all, they can hardly get mad at you for playing along with something that they started. And in the unlikely but increasingly less-unbelievable case that they're serious, well... you've always wanted to have sex with two women at the same time, and you have to admit that your mother and sister are both very attractive. It's a win-win for you—or at least win-not lose, which is almost at good.

"All right," you say to them, with a flippant air that you hope masks your inner excitement. "In that case I'll claim you both, how about that?" You wave the ticket at them mockingly.

Dana crosses her arms and grimaces. "Can't believe my own brother is doing this to me," she mutters sotto voce, before continuing at a normal volume, "Fine, whatever, let's get this over with."

Erin looks like she agrees with Dana's opinion, but only says in a level voice, "Okay, John, if that's really what you want, we're both yours to use. What do you want us to do?"

"Hmm, where to begin..." All right, now they've called your bluff. The only move left is to escalate further. "Off with your shirts!" you exclaim with a dramatic flourish, like you're the Queen of Hearts in some pornographic remake of Alice in Wonderland.

To your surprise, your mom simply goes ahead and pulls her shirt off over her head, folding it and placing it in the counter before turning back to you. She's wearing a black and gray patterned bra underneath, which manages to support her heavy breasts but still shows off a great deal of cleavage. Her belly is soft but not flabby, gently rounded and haloed by old faded stretch marks from her pregnancies. You've seen her midsection before when she's worn a two-piece bathing suit at the beach, but the way you're seeing it now is charged with a novel degree of sexuality.

Dana hesitates briefly but then follows suit after a moment with her tank top—and your surprise is redoubled or even tripled when you see that she's not wearing a bra at all. Her tiny tits are perky enough not to need any additional support, as you can now clearly see. They are only small conical swellings on her chest, not even large enough to be rounded on the underside. Her small pink nipples are slightly puffy, the areolas protruding outwards from the surrounding skin. She blushes slightly as she stands before you topless, fidgeting uncertainly, waiting for your next move.

You look between Erin and Dana several times, hardly believing your eyes. Your mom actually taking her shirt off at your command was surprising enough, but you can hardly believe your sister stripping bare-chested in front of you without complaint, especially given how shy she's always been about her body. When you were younger she would scream at you to close your eyes if she had to walk down the hall past your room even while she was wrapped in a towel, let alone completely topless. "That's... yes, perfect, thank you," you say to Dana, momentarily stunned. You can't take your eyes off her naked chest.

On impulse you reach out and flick one of her pointy nipples with your finger. She flinches slightly at the contact but makes no move to stop you. Her nipple stiffens after you tweak it, and the small bumps along the perimeter of her areola stand out like goosebumps, her body instinctively responding to the touch even as her mind recoils from it. You do it again on the other side, and then squeeze her breast in your hand, feeling the hard nipple against your palm, the soft swell of warm flesh and the contour of the rib cage beneath. Your mom reaches over with one hand and gives Dana's bare back a few gentle supportive strokes, but otherwise watches you impassively, neither of them saying or doing anything to stop you as you play with your little sister's tits.

After a few minutes of that you take your hand off of her chest, shifting your gaze over to your mother. Dana's little titties are a good appetizer, but you're feeling bolder now and ready for the main course of Erin's big jugs. Your mouth is dry and you have to clear your throat before saying, "Uh, your bra too, mom." You shift your weight uneasily between one leg and the other, trying to nudge your growing erection into a less uncomfortable position in your pants without being too obvious about it.

She purses her lips briefly, but only nods and says, "All right, John." She reaches back and unhooks the clasp of her bra, shrugs the straps off her shoulders, and slowly lowers the cups until her breasts are fully bared. Her slow movement is probably due more to **** on her part than intentional titillation, but it has the effect of a sensual strip tease on you regardless. She drops the bra onto the counter next to her shirt and puts her hands on her hips, standing defiantly exposed before you. Her nipples are larger and darker than your sister's, with wider areolas, shaped by the rigors of breastfeeding three children. Her tits hang heavily on her chest under their own weight, in marked contrast to Dana's firm little mounds, but are still full and round rather than saggy.

You reach out tentatively and cup one of your mother's breasts in your hand, watching her carefully for any sign of resistance, but she lets you touch her without objection. You lift her big boob up off her chest, hefting it to feel its weight and soft texture, and then the other, bouncing them in your hands as though you were juggling. Her nipples also grow erect when you run your thumb over them, pressing them to the side and letting them spring back up. You pinch one between thumb and forefinger and give it a tug, gently at first and then more strongly, until you're lifting her breast up by the nipple. Erin makes a soft sound of discomfort as you pull on her nipple, but says nothing out loud.

You let go, watching her boob smack back down onto her chest and bounce for a moment before coming to a stop. "This is real," you say wonderingly, and run your hand over your mom's back and down to her big round ass. You're finally starting to believe the unbelievable. "This is really real."

"Duh!" Dana chimes in. "If it wasn't do you really think I'd be standing here topless for you?"

"And you're... okay with it?" you press them both. To emphasize your point you let go of Erin's ass and rub your fingers down the front of her crotch instead, feeling the warmth of her body underneath the elastic fabric.

"I'm not excited about it, if that's what you're asking," your mother replies a bit sharply, but when you hesitate she quickly adds, "Not that I'm upset at you, sweetheart, I'm sorry. You won this prize, so of course you should claim it if you want to." She covers your hand with hers and presses it into her crotch more firmly. "I may not be happy with the idea of this contest to begin with, but I shouldn't take that out on you. I'll let you do anything to me that you're entitled to do. We both will," she adds, giving Dana a pointed look.

Your sister lets out a long-suffering sigh, but then nods grudgingly. "Yeah, yeah, whatever. I still say this is kind of gross, but fair's fair, you can use me too. But this is a one-time deal, all right?" She wags a finger in your face in emphasis. "And only because you have that stupid ticket. I'm not taking my top off for you ever again after this!"

"That's... of course, no, I understand," you say, mind blown for the second time today. That clinches it—wherever the ticket really comes from, they apparently believe it, and now you're convinced too. There's no way your loving mother would ever smush your hand against her pussy just for a joke, or let you play with Dana's tits without complaint, or her own. This is real. This is for real!

You laugh out loud, momentarily giddy with the possibilities. "I guess I'd better make the most of my prize while I can, then, huh?" They share a glance at each other and then look back at you, waiting to see what you want.