Final answer:
In kinship charts, the forked lines indicating the relationship between two entities are known as affinal ties, representing marriage or contractual relationships, in contrast to consanguineal ties which indicate biological connections.
Step-by-step explanation:
The forked lines on the lines representing the relationship between two related entities on a kinship chart are referred to as affinal ties. These double lines depict a contractual relationship by marriage or mutual agreement, different from the single line that represents a consanguineal tie, which is a biological connection, 'by blood'. The use of forked lines, or double lines, is key in distinguishing between relationships by blood and those formed through marital or contractual agreements.