Zhuge Liang’s ancestral home is in Yangdu, Langya, Xuzhou, which is now Yinan County, Shandong Province.
The Ge family originally lived in Zhuxian (now Zhucheng, Shandong), but later moved to Yangdu County (now Yinan County, Linyi, Shandong) for some reasons. Before that, there was a family with the surname "Ge" in Yangdu. People at that time were influenced by traditional clan concepts and wanted to distinguish this family from the "Ge" surname in other counties.
Just call it "Zhuge" (another saying is that it was changed to "Zhuge" in memory of his hometown), that is, the Ge family who moved from various counties. After that, the Zhuge family gradually accepted this name and called themselves themselves.
Extended information
According to historical records, when Chen Sheng was not yet king, Ge Ying led his troops to Jiujiang, where he met Xiangjiang, a descendant of Chu State. After gaining legitimacy, he supported Xiangjiang as the King of Chu.
But then came the news that Chen Sheng had become king. Because one minister could not serve two masters, Ge Ying killed Xiangjiang again, and then returned to Chen County to see Chen Sheng and reported the matter . Chen Sheng held a grudge because of this, and later found an excuse to kill Ge Ying.
But by the time of Emperor Wen of the Western Han Dynasty, in order to record Ge Ying's contribution to resisting the violent Qin Dynasty, Emperor Wen granted Ge Ying's grandson the title of Marquis of Zhuxian (now southwest of Zhucheng County, Shandong Province) and lived here for generations. In order to express gratitude to Emperor Wen for his merits, the Ge family merged the surname "Ge" with the place name and renamed it "Zhuge". During the Eastern Han Dynasty, the Zhuge clan moved from various counties to live in Yangdu.
Baidu Encyclopedia-Zhuge Liang