In the study of science, the topic of genetics is a common one.
Genetics teaches us about the transmission of genes from parents to offspring. The genes are the factors which determine the characteristics of living organisms. When we talk of resemblance of children to the parents we are taking about the characteristics children got from their parents.
Since man is sexually reproducing, what we see in children is a contribution of the genes from the father and mother to those children. Thus even at the time of choosing partners for marriage the two should consider their characteristics to predict how their children will look like.
Some genes are dominant (more powerful) that they show higher tendencies of expressing themselves that those which a recessive.
The characteristics of Height, skin color, Eye color, skin color, face shape; general body shape, ear shape and length are determined by the genes we get from our parents.
There is another issue that we need to properly understand. In human beings it is the man who determines the sex of a child. The genes are carried on threadlike structures called chromosomes. One of the chromosome pairs is for sex determination.