The dynamical evolution of Classical Kuiper Belt Objects ( CKBOs ) divides into two parts , according to the secular theory of test particle orbits .
The first part is a forced oscillation driven by the planets , while the second part is a free oscillation whose amplitude is determined by the initial orbit of the test particle .
We extract the free orbital inclinations and free orbital eccentricities from the osculating elements of 125 known CKBOs .
The free inclinations of 32 CKBOs strongly cluster about 2 ^ { \circ } at orbital semi-major axes between 44 and 45 AU .
We propose that these objects comprise a collisional family , the first so identified in the Kuiper Belt .
Members of this family are plausibly the fragments of an ancient parent body having a minimum diameter of \sim 800 km .
This body was disrupted upon colliding with a comparably sized object , and generated ejecta having similar free inclinations .
Our candidate family is dynamically akin to a sub-family of Koronis asteroids located at semi-major axes less than 2.91 AU ; both families exhibit a wider range in free eccentricity than in free inclination , implying that the relative velocity between parent and projectile prior to impact lay mostly in the invariable plane of the solar system .
We urge more discoveries of new CKBOs to test the reality of our candidate family and physical studies of candidate family members to probe the heretofore unseen interior of a massive , primitive planetesimal .