You can't return but what is preventing them to come to your new home. Snowden's girlfriend moved to Russia and I think any of his family members can visit him if they want.
I meant that if he was willing to put his family through that much trouble, they probably weren't that close in the first place. In which case, what does or doesn't happen to family left behind isn't a large factor in deciding to defect.
Maybe the fact that because you defected, they are now in some sort of secret jail or labor camp for the rest of their lives.