  In order to understand the relationship between planet multiplicity, mass,
and composition, we present newly measured masses of five planets in two
planetary systems: Kepler-323 and Kepler-104. We used the HIRES instrument at
the W.M. Keck Observatory to collect 79 new radial velocity measurements (RVs)
for Kepler-323, which we combined with 48 literature RVs from TNG/HARPS-N. We
also conducted a reanalysis of the Kepler-104 system, using 44 previously
published RV measurements. Kepler-323 b and c have masses of
$2.0^{+1.2}_{-1.1}$ M$_\oplus$ and 6.5$\pm1.6$ M$_\oplus$, respectively,
whereas the three Kepler-104 planets are more massive (10.0$\pm2.8$ M$_\oplus$,
$7.1^{+3.8}_{-3.5}$ M$_\oplus$, and $5.5^{+4.6}_{-3.5}$ M$_\oplus$ for planets
b, c, and d, respectively). The Kepler-104 planets have densities consistent
with rocky cores overlaid with gaseous envelopes ($4.1^{+1.2}_{-1.1}$ g/cc,
$2.9^{+1.7}_{-1.5}$ g/cc, and $1.6^{+1.5}_{-1.1}$ g/cc respectively), whereas
the Kepler-323 planets are consistent with having rocky compositions
($4.5^{+2.8}_{-2.4}$ g/cc and $9.9^{+2.7}_{-2.5}$ g/cc). The Kepler-104 system
has among the lowest values for gap complexity ($\mathcal{C}$ = 0.004) and mass
partitioning ($\mathcal{Q}$ = 0.03); whereas, the Kepler-323 planets have a
mass partitioning similar to that of the Inner Solar System ($\mathcal{Q}$ =
0.28 and $\mathcal{Q}$ = 0.24, respectively). For both exoplanet systems, the
uncertainty in the mass partitioning is affected equally by (1) individual mass
errors of the planets and (2) the possible existence of undetected low-mass
planets, meaning that both improved mass characterization and improved
sensitivity to low-mass planets in these systems would better elucidate the
mass distribution among the planets.
