The phenomenological sum-rule-based approach is used to discuss the quark composition dependence of some static electroweak characteristics of nucleons.The role of nonvalence degrees of freedom (the nucleon sea partons and/or peripheral meson currents) is shown to be important to select and make use of the relevant symmetry parametrization of hadron observables.The implication of hidden strangeness of the nucleon for the recently observed OZI-rule violation in antinucleon-nucleon annihilation reactions is pointed out and discussed.