Yes it is possible but not straightforward. You are trying to do a catalog type merge which is also known as a "many to one" merge.
I would recommend you have a look at Graham Mayor's website and get hold of his addin which addresses this problem.
Merge Many To One
You could also learn a lot by reading the post that Macropod has pinned at the top of the Mail Merge forum - see
https://www.msofficeforums.com/mail-...-tutorial.html