Whether or not your ex will miss you on his birthday depends on various factors, including the nature of your past relationship, how it ended, and the current dynamics between the two of you.
If your ex has moved on and is in a new relationship or has otherwise emotionally detached from your previous connection, it is possible that he may not miss you on his birthday. People can experience a range of emotions after a breakup, and sometimes they may be focused on their new life or new relationships.
On the other hand, if your ex still has feelings for you or has fond memories of your time together, there's a chance he might feel a twinge of nostalgia or miss the connection you once had, especially on special occasions like birthdays.
However, it's essential to remember that speculating about someone else's feelings can be challenging and often inaccurate. It's best to focus on your own well-being and personal growth rather than dwelling on what your ex may or may not feel. If the two of you have moved on, it's generally healthier to respect those boundaries and concentrate on building a fulfilling life for yourself.