You sound jellus @Chickenshwarmamarma ! 
People can have as many bedrooms as they want. It's up to them. My older DC has just her and her DP in a 4 bed house, with 3 reception rooms, a nice bathroom, a study, a conservatory, a cellar, a dining room, a utility room, and a large kitchen. Why? Because they can afford it, and it's what they want.
Obviously if it's social housing, a 5 bed for a couple who have 2 children just half the week would be batshit, and a 2 bed would do. But if they've bought it
it's nothing to do with anyone else.
Puzzled as to why two thirds of people think YANBU, but most comments think YABU. Baffling! 
I am laughing at the competitive bedrooms oneupmanship on here though. One poster claims to have a 7 bedroom house, so another poster trumped it with a claim of an 8 bedroom house. 😆
Anyone got a 9 bed??? Come on! 😂