Only one kernel for two data sets in scatter-histogram?

Each data set (only two) is displayed in different colors within the scatter plot and on the y-axis kernel, however the x-axis kernel only displays one data set?? I am using the code below:

figure
xA(:,2)=1;
xB(:,2)=2;

      species=vertcat((xA(:,2)),(xB(:,2)));
      x=vertcat((xA(:,1)),(xB(:,1)));
      y=vertcat(yC(:,1),yD(:,1));

     scatterhist(x,y,'Group',species,'Kernel','off','Color',[black;red],'LineStyle',{'-','-'},'Marker','.','MarkerSize',10,'Legend','off');
        xlim([-2 1]);

I would appreciate any help here. Thanks