Q: Do i own the copyrights to my photographs?

A: Absent (a) an employee-employer relationship or (b) a written agreement, signed by both parties, describing the photographs as works "made for hire," photographers retain the entire copyright interest in their works. Depending on the creative contribution of the subject, there is an argument that you could be joint authors of the photographs, but that is unlikely in this scenario.

It's best for photographers to have written agreements with their clients, determining the rights and interests of each party. The subject of your photographs can do whatever they want in the same way that someone can steal a candy bar from a grocery store; if they're not caught or no one bothers to punish them for their actions, it's of little consequence. What I mean to say is, if you don't do anything, the subject of your photographs can do anything with them, no one else is going to stop them.

Is it practical to sue someone for copyright infringement when you haven't registered the work with the U.S. Copyright Office and they're only using photographs on their personal social media accounts? You would have to ask your attorney. But, you'd only be entitled to recover "actual damages," which are generally difficult to prove and low in value in scenarios like this. You also would not be entitled to cover court costs and attorney fees without registering the work with the U.S. Copyright Office.

Do you have a legal basis to ask this person to either remove the photographs or pay for them (or both remove the photographs and pay for them)? Yes.