A more thorough explanation:

MATERNA MATERNIS

Materna maternis means that goods or property acquired through the mother are passed down to her relatives. This phrase is often used to distinguish between the inheritance rights of half-brothers who share the same mother and those who do not.

For example, if a woman inherits a piece of land from her mother, her children and siblings on her mother's side would have a claim to that property. However, her half-brothers on her father's side would not have a claim to it because they are not related to the mother.

Another example would be if a woman inherits a valuable piece of jewelry from her mother. Her maternal cousins would have a stronger claim to that jewelry than her paternal cousins because they are related to the mother.

These examples illustrate how materna maternis works in practice. It is a way of ensuring that property and goods stay within the family of the mother's side.