I went to school with a guy who had a huge package -- and had no idea he was well-endowed.
His penis wasn't that much bigger than most guys when soft. It was very thick, much thicker than most. And it had a huge amount of wrinkled skin around the shaft. But his cock, when flaccis, was maybe three inches in length. He had a very dense, fluffy pubic bush, and that tended to hide what length he had.
He was a shy person, and private about his sexuality and sex drive. If a bunch of guys got together to have beers and pass around Penthouse or watch a straight porn film, most of the guys would masturbate in front of each other. The most I ever saw him do is squeeze his enormous cock through his boxers. If someone was in the swimming pool or gym shower and got semi-erect or fully erect, he'd blush and rush out before his own penis stiffened.
But I saw him fully erect twice. Once, he was very drunk and at a party. By 4 AM, most everyone else had fallen asleep or passed out. He ended up in an upstairs bedroom, alone. I went looking for him -- hoping against hope I could get him to make out. Instead, I caught him in a guest room, pants around his ankles, moaning and stroking his huge member. His penis was easily in the 8 or 9 inch range, probably close to the latter. It was jaw-breakingly thick. It was very clear that he drew immense pleasure from his erection, because even though he was barely caressing himself he was trembling and moaning and trying to avoid ejaculating. His cock must have been stunningly over-sensitive, because I watched him bring himself to orgasm twice in the space of just a few minutes -- once by barely touching himself, and the second time by masturbating furiously.
I saw him fully erect again in a shower. He didn't realize that the shower curtain had pulled back some, allowing an observant young man to watch him. He shampooed his hair and soaped his upper body while his massive prick stabbed foward from his body. The power of his erection was so strong that his cock did not hang downward, as it does in so many ultra-well-endowed men, but instead jutted outward. Blazing red. Throbbing. I swear that I saw steam coming off his red-hot cock. When he reached down to soap up his cock and balls, he barely suppressed his moans. And again, it didn't take him long before just some gentle caressing of his shaft and knob brought him off to a powerful, 15-stream, jetstream orgasm.
I never did figure out his sexuality. He seemed immensely uninterested in women, but also evinced no interest in men. I never once caught him stealing a glance at a good-looking man. It may be that he just had no sex drive whatsoever, and was so introverted that sex or lust was not part of his personality. He jacked off, as nearly all young men with any natural amount of hormones do, but that was all.
It's too bad. He would have made a spectacular husband.