As stated before, it depends on many circumstances and no general recommendation can be given. In this comment I want to change the perspective. Most former owners are eager to help with the post-merger integration and stays for a limited time at the buyer. However, at some point former owners oftentimes want a “final cut” and move on, especially if the family business is acquired by a much bigger company as stated in the question. One reason is the difference in management style of a family-owned business and a large listed corporation.