The names are not personal, but designate families. The seal of the high-priestly house of Seraiah was probably appended either by Ezra or Eliashib, both of whom belonged to it.

(10:3-10)
At the head of the signatures stood Nehemiah the Tirshatha, as governor of the country, and Zidkijah, a high official, of whom nothing further is known, perhaps (after the analogy of Ezra 4:9, Ezra 4:17) secretary to the governor. Then follow (in vv. 3-9) twenty-one names, with the addition: these, the priests. Of these twenty-one names, fifteen occur in Nehemiah 12:2-7 as chiefs of the priests who came up with Joshua and Zerubbabel from Babylon, and in Nehemiah 12:11-20 as heads of priestly houses. Hence it is obvious that all the twenty-one names are those of heads of priestly classes, who signed the agreement in the names of the houses and families of their respective classes. Seraiah is probably the prince of the house of God dwelling at Jerusalem, mentioned Nehemiah 11:11, who signed in place of the high priest. For further remarks on the orders of priests and their heads, see Nehemiah 12:1.