how to combine two datasets and their xmls. 

Hi,
I have converted two images and two xmls to 416 x 208 size.
Now I want to combine two images into one , so it will be one image with size 416 x 416 and I also want to merge their bounding box values from two xml files into one new xml file. How I can do this task?

Waiting for your reply. Thank you very much.