For some reason the most popular video I have, even more popular than the first video I uploaded, that is over a year old, this is only 3 months old.
Some people don't believe me, oh well never mind. My penis is too long for my scrotum, which in turn was always too small for the size balls I wanted.
XXY boys start puberty normally, or within the normal range, but quite soon after they experience testicular atrophy (shrinkage) which means they don't produce an ever increasing level of testosterone.
By the time children enter puberty their bodies are primed to grow in response to sex hormones. However if puberty is stalled, or it's onset delayed for quite some time, the potential for genital growth is limited. Basically the bodies cells are most capable of responding to sex hormone when we're chidren, and less capable when we're adults.
The scrotum in males is the first organ to respond to increased testosterone, if delays occur the window for the maximum possible change is shortened. If sex hormone at the right level is not received by a predetermined but individual point of time, no further growth will be experienced.
The same is true for the penis, and the prostate gland.
I began puberty earlier than most of the boys in my year. I first noticed change myself at age 11, although there must have been changes I did not notice before then. The testosterone my testes produced was sufficient to cause the same degree or growth as in my younger brother, who is fertile and not XXY. So penis size appears to be primarily by genetic cause, and if you're bigger than average you did nothing in yourself to cause that, the same as if your penis is shorter than average.
However; if you had/have a disease that delayed or stalled puberty, it MAY be that greatly increasing your level of testosterone therapy WILL cause your penis to grow to it's greatest potential?
Please do remember though, "It's not how big you make it; but how you make it big, that counts"