Is it necessary to have more than one tree in order for pollination to occur, and if so, do peach trees come in male and female genders or does one tree contain both male and female attributes?

The vast majority of peach trees varieties are self-fertile, meaning each flower has viable and compatible male and female parts.

There are a few varieties such as J. H. Hale that have sterile pollen and require pollen of another variety for successful fertilization. And there are some varieties that have better fruit set if another variety is blooming nearby so that bees are carrying better quality pollen.