They travel to Delvile Castle , where Cecilia finds Mortimerâ s behavior yet more confusing , and Mrs. Delvile makes clear to her that she does not want Cecilia to marry her son . She is revered by her son , and she and Cecilia develop a strong and mutual regard for each other . Cecilia finds her company refreshing after living with the Harrels Mortimer Delvile : The Delviles ' son ; often referred to as `` young Delvile . ''