Young neutron stars (NS) of our Galaxy in the evolutionary stage before the death line can be divided into two groups: normal pulsars and magnetars with magnetic fields log(B)̃11-13 and log(B)̃14-15 respectively. The average magnetic fluxes (G cm2) of these groups are overline{log(Φ)} = 23.9 for normal pulsars and overline{log(Φ)} = 26.8 for magnetars. Massive OB stars, precursors of neutron stars, also can be divided into two groups: magnetic stars with average magnetic fields from several hundreds gauss to tens of kilogauss and non-magnetic or weakly magnetic stars, whose magnetic fields can not yet be measured accurately. The average magnetic flux of weakly magnetic stars can be estimated using recent measurements of the magnetic fields of selected A and B stars: Vega, Sirius A, and others. For such stars mean magnetic flux overline{log(Φ)}= 23.8 is close to the corresponding value for normal pulsars, whereas the average magnetic flux of magnetic OB stars is similar to that for magnetars. For this reason we assume that normal pulsars are descendants of weakly magnetic stars, and magnetars are progenitors of magnetic OB stars. The fraction of magnetars among NSs is only 1%, in contrast to the 7% fraction of magnetic stars among OB stars. The relatively small fraction of magnetars among neutron stars can be explained by their short lifetime.