You are a:
I sound like I'm near where a staircase once went,
It reminds me of the spiral staircase which forms an illusion of a black hole at the center from the top.
Or guarding a place that's impossible to reach.
No one has gone inside a Black Hole as it does not let even the light to escape through it.
Only Cooper & Co. from Interstellar movie can answer this from the Tesseract. I don't have a bookshelf here.
But I'm really a creature that you've never seen:
Blackholes are subordinates of the galaxy. No one has seen it through the naked eye but Event Horizon Telescope could get only a blurred version of the first Black Hole seen.
My home is remote as it's possible to be.
If you are considering the Tesseract to be the home then it lies outside the 3 dimensions we live in. It is light-years away from us. Trillions of Kms away from us.
Though I really exist, and so does my home!
That is the home described as per the Interstellar movie itself with the black hole guarding it.
Family's a mystery, I'm so small and different.
Black holes are part of the Cosmic family, members of which are being discovered daily because of its mysterious nature. There are smaller versions of Blackhole too apart from massive. Relatively they are smaller when the other structures are compared with https://en.wikipedia.org/wiki/List_of_largest_cosmic_structures. Black holes are different than planets and other general objects in the Universe.
You can't reach the answer
Yes! Black Holes cannot be reached by our current technology.