What do you atheists feel about your relatives not existing at this moment?

Yes, it bothers me. Not a day goes by when I do not miss my mother and father.

But you know what would be worse? That I would be delusional enough to think that they are in some crazy after-life.

I honor their memory by respecting their life and living up to what they would have wanted for me.

I have descendants that don't exist at the moment.
Not existing is no big deal, even god can do it.

It doesn't bother me, actually. That includes my parents, grandparents, most aunts and uncles and one (out of three) sisters. My sister died when I had just turned four and my dad died a few days before Xmas the same year (about eight months after my sister) so I had plenty of reason to think about and deal with death at an early age.
Such is life.

Of course it bothers me. I take solace in the fact that it does not bother them. As they are dead they no longer feel anything. In the words of Ricky Gervais: "When you are dead, you do not know you are dead. It's only painful & difficult for others. The same applies when you are stupid."

Sure, in some cases it hurts to think of my loved ones no longer existing. But that's life. Life is indifferent to how any of us feel about death. It happens regardless of whether or not you can deal with it.
Something better to think about is how much time I have left before I no longer exist, and how best to utilize that time.

That's how the universe works. A reminder to live life while you are alive and not put time and effort into unsubstantiated "who cares if not true? Makes me feel better" myths

They are still with me in my memories and thoughts and you actually know very little about Atheism and their perspectives. I just don't expect them to sit in some limbo waiting for me to pass so that I can feel better about dying like Theists seem to do.

Rufus exists.

Doesn't bother me. It was sad when they died but I've had time to get over it.

My family who have died have ceased to exist but they are still alive in God's memory and at the appointed time will be resurrected back to life on earth in God's Kingdom. The Scriptures say that God is not a God of the dead but a God of the living for all are alive to him.