We present optical and near-infrared photometric and spectroscopic observations of the fast-declining Type Ia Supernova (SN) 2015bo. SN 2015bo is under-luminous (M\(_B\) = -17.67 \(\pm\) 0.15 mag) and has a fast-evolving light curve (\(\Delta \mathrm{m}_{15}\mathrm{(B)}\) = 1.91 \(\pm\) 0.01 mag and \(s_{BV}\) = 0.48 \(\pm\) 0.01). It has a unique morphology in the \(V-r\) color curve, where it is bluer than all other SNe in the comparison sample. A \(^{56}\)Ni mass of 0.17 \(\pm\) 0.03 \(M_{\odot}\) was derived from the peak bolometric luminosity, which is consistent with its location on the luminosity-width relation. Spectroscopically, SN 2015bo is a Cool SN in the Branch classification scheme. The velocity evolution measured from spectral features is consistent with 1991bg-like SNe. SN 2015bo has a SN twin (similar spectra) and sibling (same host galaxy), SN 1997cn. Distance moduli of \(\mu\) = 34.33 \(\pm\) 0.01 (stat) \(\pm\)0.11 (sys) mag and \(\mu\) = 34.34 \(\pm\) 0.04 (stat) \(\pm\) 0.12 (sys) mag were derived for SN 2015bo and SN 1997cn, respectively. These distances are consistent at the 0.06-\(\sigma\) level with each other, and are also consistent with distances derived using surface-brightness fluctuations and redshift-corrected cosmology. This suggests that fast-declining SNe could be accurate distance indicators which should not be excluded from future cosmological analyses.