I got two ducks back in May, one male and one female. They were inseparable until something got my female. My drake was so sad. 
I recently acquired (2 days ago), 4 ducks, 2 female and 2 male. They are not very nice to my original male. They charge at him and try to bite him. I cannot put the males in same pen, the two new males gang up original and bite him. How can I get them to all be friends??

It is normal pecking order behavior, but realistically you have two drakes too many. Three drakes and two hens will lead to serious overmating and fighting.