Father of the House

Proper noun

 * 1) The member of a legislative house who has served the longest collective time in office.
 * 2) The member of a legislative house who has served the longest current continuous period.
 * 3) The member of a legislative house who is the oldest.
 * 1) The member of a legislative house who is the oldest.

Usage notes
When the term "Mother of the House" is also used, the "Father" usage is restricted to male members. Both "Mother" and "Father" may or may not be in use at the same time, or may alternate in accordance with the gender of the particular single member instead of having a pair of members bestowed.