A Schematic Model of Leptons and Quarks Based on Majorana Partners
  The possible extension of generation structure is investigated on the basis of a composite model, in which leptons and quarks are composed of rishons $T$ with charge 1/3 and purely neutral $V$. In this sub-system, we regard $V$ as the origin of Majorana particles. The seesaw mechanism implies the possible existence of heavy $V$, denoted as $V_B$ in addition to ordinary $V$, denoted as $V_s$. If we regard $V_B$ as a constitute block of leptons and quarks, a new generation scheme arises. This new scheme satisfies the anomaly-free condition. 
K. Koike