  Eclipsing Compact Hierarchical Triples (ECHTs) are systems with the tertiary
star orbiting an eclipsing binary (EB) in an orbit of fewer than 1000 days. In
a CHT, all three stars exist in a space less than 5 AU in separation. A
low-mass CHT is an interesting case to understand multiple star and planet
formation at such small scales. In this study, we combine spectroscopy and
photometry to estimate the orbital, stellar and atmospheric parameters of stars
in a sample of CHTs. Using the complete set of parameters we aim to constrain
the metallicity and age of the systems. We use time-series spectroscopy to
obtain radial velocities (RVs) and disentangled spectra. Using RV modelling, EB
light curve modelling, and spectral analysis, we estimated the metallicities
and temperatures. Using isochrone fitting, we constrain the ages of the system.
We then combine observations of masses, outer eccentricities (e_2), orbital
periods and age estimates of the systems from the literature. We compare the
distributions of e_2, and tertiary mass ratio, q_3 = M_3/(M_1+M_2), for three
different metallicity ranges and two ranges of age. We estimate masses, radii,
temperatures, metallicities and age of 12 stars in 4 CHTs. The CHT CD-32 6459
shows signs of von Zeipel-Lidov-Kozai oscillations while CD-62 1257 can evolve
to form a triple common envelope. The rest of the CHTs are old and have an
M-dwarf tertiary. We find that the q_3 distribution for CHTs with sub-solar
metallicity has a uniform distribution but the systems with solar and
above-solar metallicity peak between 0.5 and 1. When dividing them according to
their ages, we found the q_3 of old systems around 0.5. The eccentricity e_2
favours a value around 0.3 irrespective of metallicity or age. The
distributions are biased by the lack of observations and observing methods and
therefore call for more observations of low-mass CHT.
