Which child gets the bigger bedroom

[Bingit]

We live in a 3 bed terraced house. The 2nd bedroom is a huge double bedroom and the 3rd bedroom is a small box room. We have DD1 who is in the big 2nd bedroom. We also have a 3 month old DS who is currently in our room, but will need his space eventually.

Do we keep her in the bigger bedroom and he gets the smaller one just for being younger? (although there's only a 1yr age gap)

Or do we have them both sharing the bigger room and keep the box room free/as a playroom for them?

I don't want any resentment in the future from either of them so want to get it fair.

We've told DS that, when the time comes, he can choose to stay in his current room or move to a bigger one - but the catch is that he will have to vacate it if we have guests staying. He thinks he'll still take the bigger room but has about a year to finalise his decision.

Totally agree with pp that eldest children often have tougher parenting with bedtime and other privileges awarded later than subsequent siblings so the bigger room has to be the payoff! (DH and I are both eldest children 😁)

They share. Until one of them iseilling to have their own room. Which will be the box room.