20 supernovae that spectroscopically match the peculiar, superluminous type Ia supernova 2003fg are studied in this project. SN2003fg is thought to have erupted at a super-Chandrasekhar mass, thus breaching the theoretical mass limit for a white dwarf. By analysing the lightcurves of these 20 supernovae, this work aims to understand what the progenitor binary systems from which the supernovae erupt looked like. A lightcurve fitting using the software snpy is performed for each supernova. Using the produced models, time of maximum luminosity, stretch and maximum magnitudes in the g-, r- and i-bands are found. It is found that subluminous supernovae might be a sign of circumstellar material surrounding the progenitor star, though some of the supernovae were superluminous and some adhered to Phillip's relationship. Substructures were found in the lightcurves, as the sampled supernovae showed clearly different behaviours in each of the three bands.