Who is older, Cao Cao or Xia Houdun?

First, Cao Cao and the two Xiahou are not cousins, but cousins at most. The Three Kingdoms: Cao Teng's Adopted Son in the Song Dynasty of Cao Cao, The Marriage between Cao Cao and Xiahou, Xia Zi Miao Cai, Dun Heyuan is a cousin, but it is not credible to say that Cao Cao is Xiahou's (from a book that is very unfriendly to Cao Cao, Pei Songzhi quoted Cao Zang Biography). Because Cao Cao married two daughters to two Xiahou's sons (the ancients shared the same surname and never got married, not to mention a cousin of Wuyi), moreover, the adopted sons of the ancients generally chose close relatives, and Cao Teng's brothers also had more than one son, while Cao Wei buried Cao Song, Cao Zhen and Coss with other "brothers" in Cao Song, which is the so-called "Cao Shi Cemetery", and the two Xiahou were buried separately.

Second, the ages of Xia Houdun and Cao Cao are not verified, and there is no official record.

Thirdly, regarding the age of Xia Houdun, the official history refers to Chen Shou's The History of the Three Kingdoms. As for the statement that Xia Houdun was born in 157, I don't know where it came from. It may be made up by Luo Guanzhong.