Not sure, but it might be due to the choices you've made before going to the island. There's one large group scene on the beach after the wedding.
Look, I have been complaining a lot, and you have been kind enough to reply. I will start the game again and see what happens. But can I totally compliment you for how each character acts with you, their personalities shine through, and they come across as real people. I don't know how many you've been with, but I am amazed at these marvellous character conversations!