No, there is no "YY gender." In humans, females have two X chromosomes (XX), and males have one X and one Y chromosome (XY). It is impossible for a human to have two Y chromosomes (YY) because the mother always contributes an X chromosome.
The presence of a Y chromosome is what triggers male development, but the X chromosome also carries essential genes. A YY chromosome combination would lack these critical genes, leading to developmental issues.
While a YY chromosome combination is impossible in humans, there are genetic conditions like XYY syndrome, where a male has an extra Y chromosome (XYY). This syndrome is often associated with increased height, but symptoms can vary greatly.
However, in some fish species, scientists have successfully created YY supermales, which are used to control invasive fish populations. These YY males are unable to produce female offspring, effectively reducing the population size.
