bash script

I'm looking to extract from a file, different usernames that have the same ID. In the output i want to see the usernames and the ID's. A sample of the file is below. The real file has thousand of lines, users and Id's. The output of this example would be user1, user3 ID 54934.

I dont care about the output format as long as it has the data displayed

54934 user1
54954 user2
54934 user3
54959 user1
42452 user4
42342 user6