I only have 1, but had 2 brothers with whom I shared a room for years. We had bunk beds and a cot, replaced by a proper bed eventually when my younger bro was big enough. Separating us due to different sexes happened when I was about 10, older bro 11/12, younger bro 8. They boys continued to share for a few more years.
We all had the same bedtime until my elder bro was 8ish but that wan't cast in stone as most of the time we were treated collectively, ie all the children (and we always had a lot of people either living with us or staying for protacted periods, often with their own children). So bedtimes tended to apply to the lot ofus - sometimes as many as 8 children with ages from 4 to 12.
Bathime happened long before bedtime, in shifts. 'Bedtime snacks' - boiled egg or cheese and crackers - a bit of downtime in the garden or quietly in the sitting room with the adults. Bedtime stories read without fail every night by mum. We took it in turns to choose.
Could you swap rooms, when the time comes? Have the 2 children in your room and you and dh go in the other room? Or maybe even turn the sitting room into a bedroom and use one of the berooms as a temporary sittingroom, until you can afford to move?