One of the ways by which these two words ''Paternal and Maternal" can be differentiated is by looking at their etymology. Paternal and maternal come from the Latin words "pater" and "mater," and both mean father and mother, respectively. The suffix -al in the two words has always been used to transform nouns into their corresponding adjectives.
Since the word paternal comes from a Latin word 'pater' which means father, the addition of the adjectival suffix -al means it is referring to anything pertaining to one's father, his relatives, etc. For instance, you can use the paternal word bond when referring to the relationship between the father and his children. It can also be used to describe certain characteristics of a father. The same explanation goes for the word maternal, just that it is referring to anything pertaining to one's mother, her genes, relatives, etc. It can also be used to describe certain characteristics of a mother.