If you are a parent, and you have been confused ever since your kids have grown up, as to why they love your parents more than you, then I think I can guess what could be the reason.
You need to take your memory into flashback mode and try and remember, why did you yourself love your grandparents more than your parents.
Your kids would have, in most likelihood stayed with your parents during their summer and Christmas vacation. During the vacation, they didn’t have to school and hence they would have woken up much later than their school time.
One of the reason your kid(s) hate you is that you wake them up very early in the morning to go to school.
You would have also got upset when your kid did not want to return to your home after the vacation was over.
Also, you would have most likely given a stare when your child dropped milk on the floor, but your parents did not mind and instead laughed at what happened.
The kid’s grandparents usually laugh a lot when kids play pranks and become naughty, but the parents are always in disciplinary mode so that they grow up as civilized adults.
Finally, I would like to add, never separate kids from their grandparents. Children need all the love from their grandparents, while they are around.