The line-up of the Younghearts changed over time, on occasions because Bobby Sanders (their manager for some years) upset, fired & hired guys.
Bobby set on a whole new group on occasions as the original group broke from his control, hence them being the New Younghearts / Kings of Hearts on some recordings.
The Imperial Wonders from Cleveland were even hired by Bobby to become the group after Ron Preyer & his guys went their own way (Bobby telling the Imp.W that the original group had split up but that a new 45 was due out on them). But one night both groups were playing shows in clubs on the same street in LA, the Imperial Wonders went to meet the 'original group' and when told of their situation, the Imp. Wonder's quit as the Younghearts.
Full details on the Imperial Wonders site .... https://www.imperialwonders.com/bio.html
Ron Preyer's myspace page ... https://www.myspace.com/theyoungheartsfeatronpreyer