If you ever wonder why the two brothers have the same names, here's a footnote under chapter 19 by Megajive Translations:

"At this juncture I need to explain a major plot point. The direct translation of the title of this novel is Double Cheng—referring to the two brothers. Cheng being their surname. They were given the exact same names Cheng Yi Chen in pronunciation, obviously a highly unusual practice. The written character Chen is different though. The elder brother’s Chen means ‘day’ while the younger brother’s means ‘dawn’.

The family, including Lu Feng, calls the elder brother Xiao Chen—Little Chen, a common endearing term placed in front of Chinese names."