I've been watched Kareshi Kanojo no Jijou ("His and Her Circumstances", Kare Kano for short) lately, and the whole Tiefling thing reminded me of one of the main characters, Arima. Arima starts off as this perfect guy: handsome, popular, top student of the class, and involved in tons of extracurricular stuff. The kind of guy the rest of us hate
As we find out more about him, though, it turns out that he was abandoned by his parents, who were nothing to be proud of. They were crooks, and even hit Arima when he was a small boy. And before Arima was adopted, his uncle looked at him and said he'd never become anything worthwhile, considering what his parents were like. That's what drove Arima to be so perfect at everything, in denial of everything he really wanted, because he was afraid that his "true" self was really nothing more than a no-good, two-bit punk.
You can adapt this idea for a NG Tiefling easily enough, Yig, but it would call for a more noble, charismatic, adventurous type of Rogue than a sneaky, underhanded Han Solo type.
BTW, Ren, I really liked that character background.