While I understand the positions of the two previous posters, there are elements not being considered; power, and mob mentality. In a recent local report, a few men raped a woman. The "straight" argument technically stands here, but with them being 20-somethings, and the woman being in her late 80s, sexual attraction, and arousal due to gender, are a bit tough to comprehend. Sexual acts, especially of this type, aren't always as simple, or black and white, as people like to define. So if that situation is possible, then the scenario proposed by the OP, while uncommon, could be equally plausible.