Told I was on a 'Power Trip'

[NoOneCaresInRealLife]

Son in law of my boss was annoyed at me for asking him to change what he was doing and help out and he replied with "you're on a power trip" and flung his arms wide
Aibu to think he will always have their backing and it's time for me to move on. I'm his supervisor btw

What?

Yep. If he was a regular employee, he should have been warned/dismissed for speaking to senior like that. Have you raised the issue with your boss?

Am I right in assuming your boss is the FIL of someone you line manage? If so, does the SIL have his backing and override you or are you just too intimidated to manage him in case your boss intervenes?

My advice would be proceed as you would with any other employee. If it is a regular occurrence, ask your boss to have a word with them and explain you feel the family influence may lead him to feeling he is not on a level playing field. Beware though, boss may take his side, and come for you.

Jumped up little dick who thinks he should have special treatment because mummy or daddy runs the company, he’s the one on a power trip. I’ve seen a lot of boys with this attitude having worked for a company owned by 3 brothers who at one point or another gave their sons (who’ve had no experience of even working in a business before) jobs. All of them ended up getting fired (by that I mean given more of daddy’s money to go away and set up their own “businesses” to get them out of the company’s hair).