For many yrs. I only had one DGD & one DGS from diff. familiest. I always told my GDS that he was my favorite grandson. It took him about 10 yrs. to figure out "but Grandma, I'm your only g-son". I would reply "yes, but you're my favorite". He bought it.
I always told ea. of my 3 kids that they were my fav. child. They're all very grown now but they find comfort in that idea. LOL