The mother and the two brothers would be the trust circle if I had to guess. 
Totally agree, knowing what they did themselves, they would always be suspicious since potentially anyone could treat them the same 

 I think that’s what the Tate brothers did. They just look out for each other while scamming the world. 

 Until something happens and they decide to scam the inner circle. Too much ego, greed, thinking they’re smarter