as a person who has very strained relationship with a pair of grandparents i say, yes, it can happen.
my mother's parents love my sister but hold me indifferent (the feeling is totally mutual). it's not something i assume, one can feel when someone cares or not. on the other hand my father's parents love me a lot, and while they are not indifferent to my sister, it's less of a feeling... it's something that has been aknowledged in the family for years.
loving your family doesn't always come naturally
