Similarly, suppose they need to toss him out. (Essentially he is revealed as NOT the eldest son of his father; there is another heir.) What do they do to get him out? Is there a vote, a ceremony, a ripping of insignia off of his epaulettes?
Energetic googling has revealed that all this really became an issue in WW1, when legislation was actually passed delineating the where and the when. (Essentially if you were a German, you were out.) Also more recent legislation has passed (in the 90s) about peers being tossed out if they are convicted of major crimes and so on. But so far as I can determine, before 1900 nobody much cared. Could it really never have happened? Finding a case from which I could steal data would be fine.