It is not a good practice to combine two names while naming a child. You may choose one of the two names. You would join the father's name to his name: So, when you name a child Haroon Muhammad, it would imply that he is Haroon, son of Muhammad; and Haroon Yusuf would mean that he is Haroon, son of Yusuf, etc. 2. It is good idea to suffix son's name with that of the father: Therefore, father's name is you may call him Ali Muhammad, which means Ali, son of Muhammad.
For the important points to consider while naming children, please consult the following answer.