Wasn't seyeda Zeinab born when jibraeel came to appoint Ashab e Kisa?
Seyeda zeinab is among the prophet's family and the age difference is 1 or 2 years between her brother's, hence I wonder why she is not mentioned amongst them?

The Ashab e Kisa have a very special status with Allah. They have been defined as the five. Lady Zaynab (a) was probably born when the Kisaa’ event happened, but she may have been an infant. We don’t have any narrations that states she is part of Ahl e Kisa. While she has a great status, the status of the five is much higher.