UBVI CCD photometry has been obtained for a region around the Wolf-Rayet star WR 12. We found two young stellar associations in the observed field: the nearer one comprises the field members of Vela OBI association at d = 1.8kpc, while the farther one is the young open cluster Bochum 7 (Bo 7) at d = 4.8kpc. The stars associated with Bo 7 showed no central concentration which suggests that Bo 7 is not a young open cluster but simply a local concentration in the density of young stars belonging to the OB association (Vel OB3). These two associations have similar ages but remarkably different mass function slopes ($Gamma$ = -2.1 $pm$ 0.3 for Vel OBI and -1.0 $pm$ 0.3 for Bo 7). The stars in Vel OBI shows an evident age spread (${Delta}T~ 9Myr$). We also found two strong H$alpha$ emission stars - WR 12 and $sharp$1066 - from narrow band H$alpha$ photometry.