  We study multi-hadron systems with a single heavy quark (charm or bottom) in
the limit of heavy quark mass. The spin degeneracy of the states with quantum
numbers $(j+1/2)^{P}$ and $(j-1/2)^{P}$ for $j \neq 0$, known in a normal
hadron, can be generalized to multi-hadron systems. The spin degeneracy is the
universal phenomena for any multi-hadron systems with a single heavy quark,
irrespective of their internal structures, including compact multi-quarks,
hadronic molecules and exotic nuclei. We demonstrate the spin degeneracy in the
hadronic systems formed by a heavy hadron effective theory; $P^{(\ast)}N$
states with a $P^{(\ast)}=\bar{D}^{(\ast)}$, $B^{(\ast)}$ meson and a nucleon
$N$, and a $P^{(\ast)}$ meson in nuclear matter.
