Actually according to RAW the only way you could use "strong family ties" as both a positive and a negative feature would be if you took it twice, once as each. Page 25 states quite clearly that features are either positive or negative. RAW does not support a feature being both, it is either designated as positive indicated with +, or negative indicated with -.
So using strong family ties to give a negative die when recognizing a zombie cousin *and* using strong family ties to give a positive die for egotiating with an uncle is wrong use of the feature.