Board Thread:Questions and Answers/@comment-28002334-20140405173059/@comment-8505655-20140405233241

I doubt it. Serena and Bellicus exist even when Ben is not in the form of Alien X - judging by their dialogue, they're much older than Ben or the Omnitrix. Therefore, they would still be present even if Ben were not in the form of Alien X, and Alien X's power would still be partially theirs. Since it's very unlikely that they would allow a such power to be used solely by Ben, I would say that, no, Ultimate Ben has no more control over Alien X that regular Ben.