Hello, I am happy to answer your question. The characters in your dreams are usually symbolic.The person represents a quality or characteristic that you associate with them. Think about your relationship with your friend. What are the qualities that come to mind when you think through your relationship with him? When he shows up in your dream next time, think about how those qualities are coming into play in your life.
Marriage in a dream suggests a union or a new commitment in life. It could be, that since he is about to go off to college, you are reflecting on the strong bond/commitment you have to each other; and on the qualities that you wish to keep in your life.
Please let me know if you have questions or details you wish to discuss further. Thank you.