The general trend in the properties of elements of carbon family shows that, with the rise in atomic number.

The tendency to show +2 oxidation state increases as we move down the group. This is due to inert pair effect which causes the inability of ns² electrons of valence shell to participate in bonding.

Thus, the stability of elements in +2 oxidation state increases as we move down the group in the order C<Si<Ge<Sn<Pb, which is also due to an increase in the atomic number.