In the third part of our photometric study of the star-forming region NGC 346/N 66 and its surrounding field in the Small Magellanic Cloud ( SMC ) , we focus on the large number of low-mass pre-main sequence ( PMS ) stars revealed by the Hubble Space Telescope Observations with the Advanced Camera for Surveys .
We investigate the origin of the observed broadening of the pre-main sequence population in the V - I , V CMD .
The most likely explanations are either the presence of differential reddening or an age spread among the young stars .
Assuming the latter , simulations indicate that we can not exclude the possibility that stars in NGC 346 might have formed in two distinct events occurring about 10 and 5 Myr ago , respectively .
We find that the PMS stars are not homogeneously distributed across NGC 346 , but instead are grouped in at least five different clusters .
On spatial scales from 0.8 ^ { \prime \prime } to 8 ^ { \prime \prime } ( 0.24 to 2.4 pc at the distance of the SMC ) the clustering of the PMS stars as computed by a two-point angular correlation function is self-similar with a power law slope \gamma \approx - 0.3 .
The clustering properties are quite similar to Milky Way star forming regions like Orion OB or \rho Oph .
Thus molecular cloud fragmentation in the SMC seems to proceed on the same spatial scales as in the Milky Way .
This is remarkable given the differences in metallicity and hence dust content between SMC and Milky Way star forming regions .