Stephson being scared

So..

I was wondring.. One of my stephchildren is scared of litterally everything.. But most of all he's scared of going upstairs by himself.. He is already 10 years old and when we send the kids upstairs to get themselves washed we expect them to do it alone. Since there are 3 kids it's not always possible to join him and since he's 10 "monster sprays" won't work... If we send more than 1 kid up it's always a fuss.. They play and fight and they make a lot of noise which can't be tolerated because the neighbours' little girl (4 yo) sleeps right next to our bathroom.

I'm at a loss... if we 'force' him to go upstairs by himself he starts crying and making SO much drama.

We tend to punish him because he has confessed that he OFTEN creates such drama to just get his way..

He's been getting away with the drama until he was 9 when he confessed he's been doing it on purpose... So it's become a habit but it's a real pain.. Definitely because you can never know wether the drama is a real 'panic attack' or just the drama he creates on purpose.

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Update:

Yes.. He tells us it's because his older brother watches scary things on his tablet.. But he chooses to watch along.. Nevertheless it's mainly a problem to go upstairs or downstairs to do things he doesn't prefer to do.. It's never a problem if it's for something fun or if a cat goes upstairs and he wants to get them or to put away his socks (he has a bit of a sock phobia, which I'm not sure is a real thing but ok we kinda go along with that... He's ok with wearing my socks but if I would take the exact same sock from his drawer he'd fuss about it, he just likes having the exceptional 'special thing' that only he is granted 🙄 but ok I stopped sharing my socks and trying to find a solution for his socks and we're now making him wear his socks and he can (will) only 'tolerate' them for school.. So we're kind of just allowing that)

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Update 2:

He watches the scary stuff with his brother at their mom's place so we have no control over it. (they have no tablet here, only a laptop that is supervised and restricted) We told him he should not watch along with his brother and his brother told us he asks to put on things that aren' t appropriate for his age (not only scary movies but porn as well...) and he complies because he wants to watch that too (we kinda cringe about the thought of 2 brothers watching porn together but obviously we can tell them not to do it but it's out of our control because the tablet isn't ours, and mom is choosing not to handle it, yes, as responsable adults we told her.)

Obviously as he has no issue to go upstairs to do fun stuff we are assuming it's an act to get his way just as he's confessed he's done regularly before.