Laravel minmum characters on condition ( depends on condition )

I have a scenario that the field should have min:5 only if another request field exists? Not required_if. Like if I have a products return reasons : if the user chooses a reason and wants to add some details to the textarea (input ) so I do not need any minimum characters, while if he chooses ( Other ) reason, I do need at least 5 chars?

Here is my validation rule :

'item.*.reason' => ['required_if:item.*.selected_reason,other','nullable','min:5','max:3000']