Age estimation is a complex issue of multiclassification or regression. To address a common problem of uneven distribution of age database, this paper shows a hierarchic age estimation system, comprising age group and specific age estimation. In our system, two novel classifiers, Sequence K-Nearest Neighbor (SKNN) and Ranking-KNN, are introduced to predict age group and age value respectively. Notably, Ranking-KNN utilizes the ordinal information between samples in estimation process rather than regards samples as separate individuals. Tested on FG-NET database, our system achieves 5.37 evaluated by MAE (Mean Absolute Error) for age estimation. And the comparison between our solution and others is also shown.