  Modeling of the trajectories of VLBI components ejected by the nucleus of
1928+738 shows the VLBI jet contains three families of trajectories, i.e. VLBI
components are ejected from three different origins. The fit of components C1,
C6 and C8 indicates that the nucleus of 1928+738 contains two binary black hole
systems. The first binary black hole system is associated with the stationary
components Cg and CS and is characterized by a radius $R_{bin,1} \approx 0.220$
mas; both black holes ejected VLBI components quasi regularly between 1990 and
2010. The second binary black hole system is not associated with stationary
components and is characterized by a radius $R_{bin,2} \approx 0.140$ mas; it
ejected only three VLBI components between 1994 and 1999. The two black hole
sytems are separated by $\approx 1.35$ mas. We briefly discuss the consequences
of the existence of binary black holes systems in radio quasars to make the
link between radio quasars and GAIA.
