Cat scared of bedroom?

We have 2 cats, they are 1 year old brother and sister. Up until recently they would both jump up on to the bed in the evening and morning to see us, sleep on the bed or windowsill and use this room during the day.

However for the past fortnight our little guy won't come in the room, and if he does he creeps in the door and leaves sharpish or dives straight for the windowsill and stays up there looking at the doorway. Any noise and he runs.

There's nothing new in the room, nothing noisy that might have gone off to scare him so we really can't work out why he suddenly dislikes the room. Our little girl still comes in all the time and spends the entire night sleeping at the end of the bed. Any ideas how we can help him to be less scared?

Possibly something happened in the room while you were not there.  I would try carrying her into your bed and offering her yummy treats or playing with her on the bed.  Changer her opinion of the space by showing her fun and yummy things.  It may take a few tries.  Make the room fun and don't act differently or she will pick up on it.