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High-precision planetary densities are key to derive robust atmosphericproperties for extrasolar planets. Measuring precise masses is the mostchallenging part, especially in multi-planetary systems. We measure the massesand densities of a four-planet near resonant chain system (K2-32), and a young($\sim400$ Myr old) planetary system consisting of three close-in small planets(K2-233). We obtained 199 new HARPS observations for K2-32 and 124 for K2-233covering a more than three year baseline. We find that K2-32 is a compactscaled-down version of the Solar System's architecture, with a small rockyinner planet (M$_e=2.1^{+1.3}_{-1.1}$~M$_{\oplus}$, P$_e\sim4.35$~days)followed by an inflated Neptune-mass planet(M$_b=15.0^{+1.8}_{-1.7}$~M$_{\oplus}$, P$_b\sim8.99$~days) and two externalsub-Neptunes (M$_c=8.1\pm2.4$~M$_{\oplus}$, P$_c\sim20.66$~days;M$_d=6.7\pm2.5$~M$_{\oplus}$, P$_d\sim31.72$~days). K2-32 becomes one of thefew multi-planetary systems with four or more planets known with measuredmasses and radii. Additionally, we constrain the masses of the three planets inK2-233. For the two inner Earth-size planets we constrain their masses to besmaller than M$_b<11.3$ M$_{\oplus}$ (P$_b\sim2.47$~days), M$_c<12.8$M$_{\oplus}$ (P$_c\sim7.06$~days). The outer planet is a sub-Neptune sizeplanet with an inferred mass of M$_d=8.3^{+5.2}_{-4.7}$ M$_{\oplus}$(M$_d<21.1$ M$_{\oplus}$, P$_d\sim24.36$~days). Our observations of these twoplanetary systems confirm for the first time the rocky nature of two planetsorbiting a young star, with relatively short orbital periods ($<7$ days). Theyprovide key information for planet formation and evolution models of telluricplanets. Additionally, the Neptune-like derived masses of the three planetsK2-32 b, c, d puts them in a relatively unexplored regime of incident flux andplanet mass, key for transmission spectroscopy studies.

Masses for the seven planets in K2-32 and K2-233. Four diverse planets in resonant chain and the first young rocky worlds