Is it not the case that kale, broccoli, cauliflower and cabbage are all basically derived from the same plant?

This is what I've been told, but I am very ignorant of such matters and while you will say that I can simply Google the issue, which is true, it's never been enough of a priority for me to do so, goddammit.

As for Sequoia sempervirens or Sequoiadendron giganteum being forms of broccoli, I do in fact know enough dendrology to know that it's bullshyte.