Don't beat yourself up. I think there are a lot of hidden things that individuals will never know.
The best we can have is a healthy suspicion. In meetings we only hear people's words. We do not actually see their actions so you have to take it all with a grain of salt. Knowing what people say is different from knowing who they are.
On the other hand, I also think it is harder to see those people close to us. Having a sponsee live with you probably made the deceit easier. (That is perhaps why a distance between sponsor and sponsee is encouraged.)
Why are you in this group?