I was the favorite.
I was the only grandchild for 12 years. In their eyes, I was perfect & could do no wrong because I was the only one.
But when I was 12, they went from 1 grandchild to 5 in a matter of 18 months and were up to 8 within a couple of more years. They saw my cousins as louder & more exhausting than they remembered me being. I suppose they really were louder & more exhausting, but only because there were so many at once. Plus, my grandparents were now a decade older & slower, and none of this grandparent stuff was new anymore. They thought I was smarter & better behaved than my cousins, but I wasn't. There was just 1 of me and it was all new to them.
And that continued all the way into adulthood:
Getting my drivers license
Graduating from high school
Graduated from college (first in my entire family)
Getting a real job
Getting married & having my own family
My grandparents were overjoyed as I reached these milestones and were so proud they couldn't hide it. They tried to help financially on things like my 1st new car & college expenses. Because I was first, and they'd never experienced anything like these things as a grandparent.
But when my younger cousins reached those milestones, there were 4 kids hitting them all at the same time and it didn't seem as special to my grandparents. They had done all this before. Plus, there were too many to really help financially. No matter what my cousins ever did, my grandparents couldn't help but look at my version as better.
It never affected my relationship with my cousins. I don't even know if anyone other than me ever noticed. But I noticed, and it always bothered me. I don't hold it against my grandparents. It's probably just human nature. They loved all of us very much, and I think they loved us all equally, but there is no doubt that I was favored in a way that the others never experienced.