  Mobile call networks have been widely used to investigate communication
patterns and the network of interactions of humans at the societal scale. Yet,
more detailed analysis is often hindered by having no information about the
nature of the relationships, even if some metadata about the individuals are
available. Using a unique, large mobile phone database with information about
individual surnames in a population in which people inherit two surnames: one
from their father, and one from their mother, we are able to differentiate
among close kin relationship types. Here we focus on the difference between the
most frequently called alters depending on whether they are family
relationships or not. We find support in the data for two hypotheses: (1) phone
calls between family members are more frequent and last longer than phone calls
between non-kin, and (2) the phone call pattern between family members show a
higher variation depending on the stage of life-course compared to non-family
members. We give an interpretation of these findings within the framework of
evolutionary anthropology: kinship matters even when demographic processes,
such as low fertility, urbanisation and migration reduce the access to family
members. Furthermore, our results provide tools for distinguishing between
different kinds of kin relationships from mobile call data, when information
about names are unavailable.
