  We compute the second moments of pion and rho parton distribution functions
(PDFs) in lattice QCD with $N_f = 2+1$ flavors of improved Wilson fermions. We
determine both singlet and non-singlet flavor combinations and, for the first
time, take disconnected contributions fully into account. In the case of the
rho, we also calculate the additional contribution arising from the $b_1$
structure function. The numerical analysis includes 26 ensembles, mainly
generated by the CLS effort, with pion masses ranging from 420MeV down to
214MeV and with 5 different lattice spacings in the range of 0.1fm to 0.05fm.
This enables us to take the continuum limit, as well as to resolve the quark
mass dependencies reliably. Additionally we discuss the contaminations of rho
correlation functions by two-pion states.
