Dependence of the absolute magnitude H on the proper semi-major axis a_p for the Themis family (left) and for the Flora family (right) with the likely positions of the family centers (vertical lines). We also plot three (a_p, H) borders of the family for different parameters C (different values correspond to a different initial extent of the family or different age and magnitude of the Yarkovsky semi-major axis drift) by gray lines, the optimal border corresponds to the middle line. The vertical dotted line represents the approximate position of the secular ν₆ resonance for the inclination typical for Flora family members and the horizontal arrow its approximate range.