He nodded his head a little when she told him not to worry, and again when she told him to warn her when he was close. Feeling her massage his cock against and into the warm moist folds of her pussy was absolutely amazing. The way her fingers worked their way up and down the shaft felt amazing in it's own right. "Okay, I'll warn you." He said with a shaky and breathy moan. His cock throbbed against her pussy, more and more pre leaking from the tip of his cock and trickling down, helping to lubricate the shaft. The wetness from her pussy was also helping in lubricating up his cock, the moisture from her folds transferring across to his rock hard erection. He instinctively began to rock and grind his hips in time with her massaging motions, but it didn't take much of that for him to realize he was about to come. "Big sister...I-I'm close..." He warned her amidst a moan, trying his best to hold off his orgasm for the time being.