1. Whatever I would write would not be rhetorical
  2. For what it is worth, I do not have the answer to the question

I wonder how it was like for you when you went for a walk with your grandfather. Or when your grandmother would give you a sound piece of advice.
I would not know how either of those emotions feels, as I never got a chance.

When was the first time you knew you loved your grandparents? You did not love them at least until you learned your mommy had mum and dad too, and you would be visiting them for the first time in the summer breaks. You did not love them just when you heard about them, or even when you saw them--come to think about it--if your parents were to point out to any person, saying that person was your grandparent; when you had never seen them before, and you "loved" them. Well, they could have pointed to anyone, and would you still "love" them? Good thing that parents do not test their kids like this.

For those who have a younger sibling, it is very likely that their birth was one of the happiest moments in your life.
But do you love someone just because you shared the same womb at one point of in time? If you were to learn you had an elder sibling, who died before you were born, and you had a valid proof that it was true, would you start loving a person whom you had never interacted with, and never will, in your life?

Would you love your sibling if they were stillborn? Would you love the sibling, who never made it, who was miscarried, or who was aborted?

Think of that kid who never saw his dad because when he was in the womb, his father had to serve in the war to defend the country, and then he was captured as a prisoner of war. The father, after suffering from post-traumatic stress disorder, spending each moment in the prison thinking and hoping that his wife lives in the same house which he called "home". To see, if had a son or a daughter,
and how they would have been doing,
and figuring out how could they possibly explain not being there in their childhood--for no fault of either of two.

If the son opens the door, and he looks just like his mother and you the war veteran knows he is his kid and says: "Son! I am your dad."
Father is in tears, but the kid, in his late teens does not believe, yet. And his mother exclaims, "Arnold! Is that you?" and she is crying too, and the kid now realises this man, in his late 50s is his father.

Most of us would not know, how it is, to see your father for the first time, when you are in your teenagehood. You know your parents for as long as you remember--including your oldest memory.

But for what it is worth, you do not love your sister because she is your sister.
You do not love your grandparents because they are [your grandparents].
You do not love your parents because they are your parents.

"Blood relative" is not a good reason to love someone. There is a lot more to it.

You may admire, appreciate, respect someone whom you have never interacted with. "Love" requires something more profoundly strong and intense than all of those put together.