  By searching the Open Supernova Catalog, an extra-galactic transient host
galaxy database, and literature analyses, I present the largest sample of type
Ia supernova (SN Ia) siblings to date. The sample comprises 158 galaxies,
consisting of 327 confirmed SNe Ia - over 10 times larger than existing sibling
SN Ia samples. SN siblings share host galaxies, and thus share global
environmental properties and associated systematic uncertainties. This makes
them valuable for both cosmological and astrophysical analyses; for example,
sibling SNe Ia allow for comparison of environmental properties within the same
galaxy, progenitor comparisons, rates analyses, and multiple calibrations of
the Hubble-Lema\^{\i}tre constant. This large sample will provide a variety of
new avenues of research, and be of great interest to the wider SN Ia community.
To give an example use of this sample, I define a cosmology sub-sample of 44
siblings; and use it to compare light-curve properties between sibling pairs. I
find no evidence for correlations in stretch ($x_1$) and colour ($c$) between
pairs of siblings. Moreover, by comparing to a comparable set of random pairs
of SNe Ia through boot-strapping, I find that siblings are no more similar in
$x_1$ and $c$ than any random pair of SNe Ia. Given that siblings share the
same hosts, differences in $x_1$ and $c$ between siblings cannot be due to
global galaxy properties. This raises important questions regarding
environmental systematics for SN Ia standardisation in cosmology, and motivates
future analyses of sibling SNe Ia.
