This is very similar to the Single Heart and the steps are very much the same.
With the double heart make to small parts instead of one larger part. Then pull the hair upward between the elastic. Do the same steps for the 2nd ponytail.
I once again rolled the hair to make it easier to manage. 
Secure the ends of each ponytail with its own elastic.
Then pull the 2 hearts together and secure with an elastic as shown below.
