  The majority of massive stars are found in close binaries which: (i) are
prone to merge and (ii) are accompanied by another distant tertiary star
(triples). Here, we study the evolution of the stellar post-merger binaries
composed of the merger product and the tertiary companion. We find that
post-merger binaries originating from compact stellar triples with outer
semi-major axes $a_{\rm out,init}\lesssim10^1\,-\,10^2\,\rm AU$ provide a new
way to form binary black hole mergers in the galactic field. By means of a
population synthesis, we estimate their contribution to the total black hole
merger rate to be $\mathcal{R}(z=0)=0.3\,-\,25.2\,\rm Gpc^{-3}\,yr^{-1}$.
Merging binary black holes that form from stellar post-merger binaries have
exceptionally low mass ratios. We identify a critical mass ratio $q\simeq0.5$
below which they dominate the total black hole merger rate in the field. We
show that after including their additional contribution, the mass ratio
distribution of binary black hole mergers in the galactic field scenario is in
better agreement with that inferred from gravitational wave detections.
