Jen Tennyson

Jennipher Jenese "Jen" Tennyson was the twin sister of Dimension 66's version of Ben Tennyson.

History
Jennipher never got an Omnitrix of her own and helped her brother, cousin, and Grampa fight against threats that nobody else could face. In one of these fight she ended up putting the Omnitrix on after her Brother was killed by another team up between Vilgax and Kevin, in which the latter crushed Ben to death after Kevin stabbed him in the back.

After that tragic incident she vowed to never let others die for the wrong cause. She never removed the Omnitrix and continued on with her life.

When she was 15 years old she had fought off a new threat who was going to destroy her Universe but failed and ended up in Ben Prime's universe where she lost most of her memories and ended up being adopted by Ben Prime's parents. After seeing all the people of her Universe in this universe, her memories came back to her and she decided to help Ben Prime out with saving the universe.