scammers on the same day. they scam my siblings

my sibling called me one day and he was crying during the call that he has been scammed, I asked why? he told me that someone introduce this app to him.that after he log in, he should fill up those gaps that it's an income app. the three of them have him 4000 each, till now no where to found the money and couldn't return the money he collected from my siblings till now. don't fall oooo. open your eyes everyone. they are scammers.