The way we use the term hook on this message board, it's rather narrowly defined. And being a twin doesn't qualify.
A hook is an attribute of an applicant that fulfills one of a college or university's institutional wants or needs. Colleges have football teams, and football teams need players. So if you're one of the most sought-after high-school running backs in Texas, that's a hook. Colleges need wealthy donors. If you come from a family that could (and would) make a seven-figure gift to the college, that's a hook. Colleges want alumni to feel kindly disposed to the college, so being a legacy can be a hook. Colleges want socioeconomic diversity, so coming from an underprivileged background or belonging to an underrepresented minority group is often a hook.
But I don't know of any college or university that has an institutional need or desire to enroll twins, so, no, being a twin wouldn't be a hook.
That doesn't mean it's completely worthless to you. Apart from the daily joy that you no doubt get from having a twin sibling, you may be able to find something in your twin story that makes you memorable to the people in admissions who read your application. You may find something in there that makes for a great essay. Being memorable is what gets your application moved from the "maybe" pile to the "yes" pile (as long as you're memorable in a good way, of course). But your being a twin won't be appealing to colleges and universities per se; you'd have to make it so.