Since each of these spawns has an independent time frame for its respawn, a situation in which two of these bosses will be online simultaneously is as possible. However, it is difficult to say whether they can literally respawn at the same time. This may be impossible to prove.
Of course, due to frequent mismatches and the issue of luck in meeting a boss, bringing about a situation where we slaughter the same boss one after the other is extremely rare, but technically it is feasible. History knows plenty of cases where the same boss fell twice on a given server on a particular day. Who knows, perhaps their respawns overlapped.
The same goes for bosses such as Rotworm Queen, Tyrn or Hirintror.