The Kα and Kβ x-ray spectra of Se, Y, and Zr were studied experimentally and theoretically in order to obtain information on the Kα1 line asymmetry and the spin doublet in Kβ1,3 diagram lines. Using a high-resolution antiparallel double-crystal x-ray spectrometer, we obtained the line shapes, that is, asymmetry index and natural linewidths. We found that the corrected full width at half maximum of the Kα1 and Kα2 lines as a function of Z is in good agreement with the data in the literature. Furthermore, satellite lines arising from shake-off appear in the low-energy side of the Kα1 and Kα2 lines in Se but, in Y and Zr, it was very difficult to identify the contribution of the shake process to the overall lines. The Kβ1,3 natural linewidth of these elements was also corrected using the appropriate instrumental function for this type of x-ray spectrometer, and the spin doublet energies were obtained from the peak positions. The corrected full width at half maximum (FWHM) of the Kβ1 x-ray lines increases linearly with Z, but this tendency was found to be, in general, not linear for Kβ3 x-ray lines. This behavior may be due to the existence of satellite lines originated from shake processes. Simulated line profiles, obtained using the multiconfiguration Dirac-Fock formalism, accounting for radiative and radiationless transitions and shake-off processes, show a very good agreement with the high-resolution experimental spectra.