)
Only one of them is an alicorn: the one to the far right (Prince Endearment). The other three are a pegasus, a ground pony, and a unicorn.
Endearment was born an alicorn. In my work, alicorns exist as a proper race of pony. However, there are only 3000 of them, and Endearment is one of few with an extreme level of power.