  Under what conditions does a superconductor inherit topologically protected
nodes from its parent normal state? In the context of Weyl semimetals with
broken time-reversal symmetry, the pairing order parameter is classified by
monopole harmonics and necessarily nodal [Li and Haldane, Phys. Rev. Lett.,
120, 067003 (2018)]. Here, we show that a similar conclusion could also apply
to 2D Dirac semimetals, although the conditions for the existence of nodes are
more complex, depending on the pairing matrix structure in the valley and
sublattice space. We analytically and numerically analyze the
Bogoliubov-de-Gennes quasi-particle spectra for Dirac systems based on the
monolayer as well as twisted bilayer graphene. We find that in the cases of
intra-valley intra-sublattice pairing, and inter-valley inter-sublattice
pairing, the point nodes in the BdG spectrum (which are inherited from the
Dirac cone in the normal state) are protected by a 1D winding number. The nodal
structure of the superconductivity is confirmed using tight-binding models of
monolayer and twisted bilayer graphene. Notably, the BdG spectrum is nodal even
with a momentum-independent "bare" pairing, which, however, acquires
momentum-dependence and point nodes upon projection to the Bloch states on the
topologically nontrivial Fermi surface, similar in spirit to the Li--Haldane
monopole superconductor and the Fu--Kane proximity-induced superconductor on
the surface of a topological insulator.
