  The study of supernova siblings, supernovae with the same host galaxy, is an
important avenue for understanding and measuring the properties of Type Ia
Supernova (SN Ia) light curves (LCs). Thus far, sibling analyses have mainly
focused on optical LC data. Considering that LCs in the near-infrared (NIR) are
expected to be better standard candles than those in the optical, we carry out
the first analysis compiling SN siblings with only NIR data. We perform an
extensive literature search of all SN siblings and find six sets of siblings
with published NIR photometry. We calibrate each set of siblings ensuring they
are on homogeneous photometric systems, fit the LCs with the SALT3-NIR and
SNooPy models, and find median absolute differences in $\mu$ values between
siblings of 0.248 mag and 0.186 mag, respectively. To evaluate the significance
of these differences beyond measurement noise, we run simulations that mimic
these LCs and provide an estimate for uncertainty on these median absolute
differences of $\sim$0.052 mag, and we find that our analysis supports the
existence of intrinsic scatter in the NIR at the 99% level. When comparing the
same sets of SN siblings, we observe a median absolute difference in $\mu$
values between siblings of 0.177 mag when using optical data alone as compared
to 0.186 mag when using NIR data alone. We attribute this to either limited
statistics, poor quality NIR data, or poor reduction of the NIR data; all of
which will be improved with the Nancy Grace Roman Space Telescope.
