Was Ruth Royal Victoria's sister and not daughter in the beginning? Yes. In the first the episode after Redd Foxx's death, Jackee was written into the series as Della Reese's sister, Ruth Royal. It was changed when people asked about the age difference between Reese and Harry. A few episodes later it was stated that Ruth was her daughter.
Did Redd Foxx die during filming of an episode. Yes, much like when John Ritter died while filming 8 Simple Steps, Redd Foxx died on set. Unlike John Ritter, who had unaired episodes already filmed, Redd Foxx's final episode aired before his death.
Warning: The Royal Family guide may contain spoilers