“I bought the session package, that means I own the photos, right?”
This is a question I see a lot. The short answer is probably not. By law, copyright ownership of an artistic creation (photography being one), stays with the creator of that art. Most photography sessions, such as maternity, newborn or family, are for personal use and do not include the copyright ownership of the images. You can, of course, buy the copyright, but that could cost you thousands of dollars…per image. Buying the copyright to an image or set of images essentially prevents the photographer from ever using that image again. It’s also not necessary. When a photographer provides a gallery of images that you have paid for, they should also provide a photographer’s release or print release. The release allows the purchaser (you) to take those digital images and put them on social media or have them printed anywhere, as many times as you like. Typically, that’s all a consumer needs.
Where you may need to purchase copyright is if you want to use the images commercially. In other words, you want to make money off the images. You can approach that two ways: you can buy a commercial use license which gives you the ability to use the images for marketing or products for a limited time or you buy the copyright outright and own it forever. Both options are going to be more expensive than getting a print release. Unless you are planning to produce products with this image, author a book with this image in/on it or use the image to make money in another way, asking to purchase the copyright is simply not needed.
Here is an excellent article by TheLawTog.com that explains the difference between copyright and print release: Copyright vs Print Release