Responses
Consider re-training sibling to come tell me straight away so I can tell her exactly what to say to her "employer"... Possibly ranging from an agry "my bro/sis says to go f*k yourself" to a milder "Ask me directly, idiot"...
P.s.: Never let idiot 3rd-guy ruin you two siblings' relationship, most of the time the younger sibling is just naive and 3rd guy's the one truly at fault.

I wish he would just ask suha shit straight up but then again I don’t see much wrong with the little sister “spying” it’s not like they’ve done anything bad tbh.
I just hope things don’t get blown out of proportion like always..