I don’t think you can compare them.
It depends on the family member, how close you were, if it came as a shock or if they lived in your home etc.
I have been more upset by my cat dying than my grandparents.
My elderly dog dying is going to be one of the hardest things I’m going to deal with.
Its not that I love my grandparents less, it’s the fact that for years my cat and dog have been there in my home every single day for years and so I feel/will feel the loss greater than someone who I see much less.
My pets are absolutely family members.
But I’m sure if I lost my DD or even my parents or siblings then I would be more upset about them, especially if they died unexpectedly/young.
I am very fortunate that I’ve only experienced older relatives dying and so I’m not able to compare the two directly, but even if I had I think they’re incomparable.
I don’t like when people feel that a pet dying deserves less grief than a human.
At work, a lady lost her dog (lives alone) and took time off due to grief and there were staff members who felt it was unfair because it was ‘just a dog’.
Fortunately, most of us including or boss didn’t feel that way and she was told not to come in and we shared her responsibilities between us.