Turn them down gently.

"No." You reply quietly. You do not pull away or make any other movement which might frighten them. "I don't want you that way."

"But we're willing." Erin replies, rubbing you with her hand. "You know you want us, Alex."

"Yes I do. But I'm not willing to have you two prostitute yourselves for protection." You reply bluntly. You hope you haven't offended, and their answering nods make you secure that you haven't.

"You really are a nice guy, Alex," Brittney smiles at you, and then leans forward to give you a lingering peck on the cheek. Her sister follows the cue, and plants one on the opposite side of your face. You sure don't feel like a nice guy. You feel like you turned down a golden opportunity.

Eventually, the two girls fall asleep again, and you free yourself from their embrace. You wonder what your next move should be. This basement won't be safe forever. Perhaps some civilization has began again outside.