  In this paper, we show that the G-normality of X and Y can be characterized according to the form of f such that the distribution of {\lambda}+f({\lambda})Y does not depend on {\lambda}, where Y is an independent copy of X and {\lambda} is in the domain of f. Without the condition that Y is identically distributed with X, we still have a similar argument. 
A note on characterizations of G-normal distribution