there were no public reports or confirmed information about Prince Charles explicitly preventing his brother, Prince Edward, from becoming the next Duke of Edinburgh. The situation may have evolved or changed since then, but without any recent updates, it's challenging to provide accurate details on the matter.
Traditionally, titles and succession within the British royal family are governed by a combination of historical rules, royal prerogative, and individual decisions made by the reigning monarch. The decision about who will inherit a particular title can be influenced by various factors, including the wishes of the reigning monarch, senior members of the royal family, and other considerations.
It is also worth noting that the British royal family generally maintains a level of privacy regarding internal family matters. As a result, specific details about the allocation of titles and the reasoning behind such decisions might not always be made public.
To get the most current and accurate information on this matter, I recommend consulting recent and reputable news sources or official statements from the British royal family and their representatives.