Just re-reading. One thing for sure, the ex husband ending was all his choice.

The first one to hate isn't the other woman, but the man who had another woman.

Also, the Emperor didn't bother to double-check if the child was really his or not...? As an emperor, he sure is easy to trick. An emperor should at least do some investigating to verify the evidence itself, more so if it concerns the imperial lineage.

At this point, failing his marriages, then losing his child is something he can only regret, after all everything was his own choice.