It doesn't say in any of the books. All you know is that they are twins and that they are older than Jacob.
Rebeca and Rachel
2 brothers and 3 sisters
Louisa Matilda Jacobs is 80 years old
Marc Jacobs is 54 years old (birthdate: April 9, 1963).
Rachel Jacobs is 47 years old (birthdate September 26, 1970).
Jimmy Jacobs is 27 years old (birthdate: February 17, 1984).
Christian Jacobs is 39 years old (birthdate: January 11, 1972).
Nancy Jacobs is 59 years old (birthdate: October 27, 1951).
A. J. Jacobs is 43 years old (birthdate: March 20, 1968).
As of the end of the 2013-2014 NFL season Tramain Jacobs is 22 years old.
As of the end of the 2013-2014 NFL season Ben Jacobs is 26 years old.
As of the end of the 2013-2014 NFL season Nic Jacobs is 22 years old.