I'm not sure what you want. However, consider using hold on in order to overlay multiple plots on an axis.
x1 = ones(1,100);
x2 = 2 * ones(1,100);
x3 = 3 * ones(1,100);
y1 = 2 * randn(1,100);
y2 = [randn(1,50) randn(1,50) + 4];
y3 = 5 * randn(1,100) + 5;
%% plotting
h = boxplot([y1, y2, y3], [x1, x2, x3]);
set(h, {'linew'},{2})
hold on
swarmchart(x1,y1,5)
swarmchart(x2,y2,5)
swarmchart(x3,y3,5)
hold off
