I'm pretty sure Chiltern began as a BR management buy-out, supported by John Laing plc.
They eventually took control, before selling on to DB Regio.
DB then transferred it to Arriva.
So 3 changes of control (and a franchise rebid).
VWC has had 51% Virgin Group ownership throughout.
Being pedantic, Chiltern's immediate parent is still M40 Trains, just as it has been since February 1995!
From a licencing point of view, the change of parent company appears to have been inconsequential, and Chiltern are still running services under the original European Passenger Licence granted in April 1995 (as are VTWC), whereas the current SWT one dates from 2007.