Question

In some human families certain characters may skip a generation or two and then reappear. why does this happen

Answer 1

because of the repression done by the dominant Gene in the first generation but in second generation it will reemrge

Answer 2

The trait and characters that sometimes do not appear in the continuous generations might be having alleles ( different genes for the same trait ). So the traits that might not have been experienced will be of the recessive genes infront of the dominant genes. Thus these genes might have just suppresed in the presence of dominant genes. However these might again reappear in successive generation as the gene is not lost but just merely suppresed.
In presence of another identical gene from the partner then these trait would reappear.