I am a chinese, from the cloth I think it is a chinese thing. I think this statue is trying to show a very famous 'filial' event/legend in chinese history. In the old time in China, two most important core moral ideas: loyalty to the emperor and filial respect to your parrents. To educate the common people, a serie of legend/events including 24 stories are formalized.
This is actually one of them, I guess, it is #17 in this serie and story is a man name Cui, shannan, his grandma is very filial, and she breast-fed her 'mother-in-law' when she is too old to eat. I guess somehow the storyline is still there, but maybe the creator of the statue or the person made caption simply made a mistake.
The sequence of these events are not fixed, here is english version of the stories, the #10 is about this.
www.ruf.rice.edu/~asia/24ParagonsFilialPiety.html
And a painting for similar theme is here: (in chinese)
www.xywq.com/xiaojing/files/f-2/24x9-29.htm