4yo won't go to sleep

[AdventuresWithVoles]

DS, last night 10pm & few other times recently.
Shares room with over-sensitive 8yoDS.
I need everyone in bed from 9pm-ish & especially me, I was so tired.
But 4yoDS would NOT stay in bed, and was whining & keeping 8yo awake.
I am not at my best when exhausted. Kept chucking 4yo back in his room & bed & then started scolding him but that upsets 8yo hugely (starts wailing hysterically if he gets too far gone, he was tired & needed sleep, too) so finally took DS outside for a cold walk until he agreed to sleep.
Not nice but I was at end of my tether.

Is there some obvious trick I'm missing for keeping them quietly in bed? DS had an hour nap yesterday (I could not prevent but he was also up at 6:30am so 9-10pm to lie down peacefully in bed should have been reasonable, no?)

Cannot have 4yo sleep in another room unless it's mine. DH was at work last night.

Might 4yo go to sleep in your bed and then you lift him when you go to bed? I sympathise, I have 2 vampires that don't sleep (9 and 4) - some nights I could scream, but I am lucky in that they do each have a room so they can get to sleep separately.

10? that's early. DD1, also 4, has made it to midnight recently. I took all her toys out her room (defeating the laws of physics by fitting them ALL into 1 cupboard!) and just kept telling her off and we are getting there slowly!

On sleepover nights, FIL sits with her 'till she falls asleep. He has the patience of a saint!

I did that for a little while, Housemum, but then he sneaks back in before morning (which wakes me up & I may not sleep at all again) & really I think he can sleep alone. Think. So I am completely banning any sleep in my bed. He would have managed to go to sleep last night quickly without the day time nap, but I can't prevent every nap. :( And it wasn't a long nap.

Ah, Gemma, at least you can commiserate. Blardy non-sleeping children.