The photographer almost certainly owns them, unless the photographer specifically gave up their copyright on them. The photographer most likely also has an agreement with the couple that allows them to use the photographs and specifies how they can use them, share them, etc., but the photographer still owns them, not the couple. The couple is just given permission to use them. That agreement might include being allowed to share them with friends and family on social media and blogs, but you would have to check to be sure. There will also likely be a requirement that the images not be altered, give proper attribution, maintain watermarks, etc.
This is applicable to America. Other places do copyright differently.