Messaging Issues

My brother and I both have IPhone 6s with At&t. My brother, dad and I use the same Apple account. My dad and I have no problems sending messages to one another. However, my brother isn't receiving my messages. We can call one another. He can send text and Imessages to me (I received them) but he can't recieve my messages I send to him. I tried sending them as text and iMessages but neither worked. We updated his phone, so we both have the most recent iOS. I don't know what to do, I am open to any help.