  Sigma Orionis is an open cluster in the nearest giant star formation site -
Orion. Its youth (3-5 Myr), low reddening, and relative vicinity make it an
important benchmark cluster to study stellar and substellar formation and
evolution. Young star-forming sites are complex and hierarchical. Precision
astrometry from Gaia DR3 enables the exploration of their fine structure. We
used the modified convergent point technique to kinematically re-evaluate the
members in the Sigma Orionis cluster and its vicinity. We present clear
evidence for three kinematically distinct groups in the Sigma Orionis region.
The second group, the RV Orionis association, is adjacent to the Sigma Orionis
cluster and is composed only of low-mass stars. The third group, the Flame
association, whose age is comparable to that of Sigma Orionis, overlaps with
the younger NGC 2024 in the Flame Nebula. In total, we have discovered 105
members of this complex not previously found in the literature (82 in Sigma
Orionis, 19 in the Flame association, and 4 in the RV Orionis association).
