Translation:My grandpa and grandma live in Beijing.
I believe it's a real rule. When my textbook taught us the word for sibling (兄弟姐妹), it said to always go in the order "male before female, then older before younger". Something about it being a holdover from a long time ago. That said, in English if you are just saying this, female-first seems to be the implied order (but not as strict a rule): "mom and dad", "grandma and grandpa", "aunt and uncle".