  Context. According to the hierarchical structure formation model, brightest
cluster galaxies (BCGs) evolve into the most luminous and massive galaxies in
the Universe through multiple merger events. The peculiar radio source 4C 35.06
is located at the core of the galaxy cluster Abell 407, overlapping with a
compact group of nine galaxies. Low-frequency radio observations have revealed
a helical, steep-spectrum, kiloparsec-scale jet structure and inner lobes with
less steep spectra, compatible with a recurring active galactic nucleus (AGN)
activity scenario. However, the host galaxy of the AGN responsible for the
detected radio emission remained unclear.
  Aims. We aim to identify the host of 4C 35.06 by studying the object at high
angular resolution and thereby confirm the recurrent AGN activity scenario.
  Methods. To reveal the host of the radio source, we carried out very long
baseline interferometry (VLBI) observations with the European VLBI Network of
the nine galaxies in the group at 1.7 and 4.9 GHz.
  Results. We detected compact radio emission from an AGN located between the
two inner lobes at both observing frequencies. In addition, we detected another
galaxy at 1.7 GHz, whose position appears more consistent with the principal
jet axis and is located closer to the low-frequency radio peak of 4C 35.06. The
presence of another radio-loud AGN in the nonet sheds new light on the BCG
formation and provides an alternative scenario in which not just one but two
AGNs are responsible for the complex large-scale radio structure
