  The Kepler mission provides a wealth of multiple transiting planet systems
(MTPS). The formation and evolution of multi-planet systems are likely to be
influenced by companion stars given the abundance of multi stellar systems. We
study the influence of stellar companions by measuring the stellar multiplicity
rate of MTPS. We select 138 bright (KP < 13.5) Kepler MTPS and search for
stellar companions with AO imaging data and archival radial velocity (RV) data.
We obtain new AO images for 73 MTPS. Other MTPS in the sample have archival AO
imaging data from the Kepler Community Follow-up Observation Program (CFOP).
From these imaging data, we detect 42 stellar companions around 35 host stars.
For stellar separation 1 AU < a < 100 AU, the stellar multiplicity rate is 5.2
$\pm$ 5.0% for MTPS, which is 2.8{\sigma} lower than 21.1 $\pm$ 2.8% for the
control sample, i.e., the field stars in the solar neighborhood. We identify
two origins for the deficit of stellar companions within 100 AU to MTPS: (1) a
suppressive planet formation, and (2) the disruption of orbital coplanarity due
to stellar companions. To distinguish between the two origins, we compare the
stellar multiplicity rates of MTPS and single transiting planet systems (STPS).
However, current data are not sufficient for this purpose. For 100 AU < a <
2000 AU, the stellar multiplicity rates are comparable for MTPS (8.0 $\pm$
4.0%), STPS (6.4 $\pm$ 5.8%), and the control sample (12.5 $\pm$ 2.8%).
