  The separate quark flavour contributions to the pion and kaon valence quark
distribution functions are studied, along with the corresponding
electromagnetic form factors in the space-like region. The calculations are
made using the solution of the Bethe-Salpeter equation for the model of Nambu
and Jona-Lasinio with proper-time regularization. Both the pion and kaon form
factors and the valence quark distribution functions reproduce many of the
features of the available empirical data. The larger mass if the strange quark
naturally explains the empirical fact that the ratio $u_{K^+}(x)/u_{\pi^+}(x)$
drops below unity at large $x$, with a value of approximately $M^2_u/M_s^2$ as
$x \to 1$. With regard to the elastic form factors we report a large flavour
dependence, with the $u$-quark contribution to the kaon form factor being an
order of magnitude smaller than that of the $s$-quark at large $Q^2$, which may
be a sensitive measure of confinement effects in QCD. Surprisingly though, the
total $K^+$ and $\pi^+$ form factors differ by only 10\%.
