Answer:
dyads
Explanation:
A dyad is a kind of group that ceases to exist if even one member of leaves the group. 
Such groups consists usually of two people. 
- A dyad is used in sociology to refer to a group of two people
- It can be a brother and a sister
- Such groups can be terminated when one member of the group pulls out or dies. 
- Dyads are the simplest group structures known. 
- Members of a dyad can be linked by education, romance, business, e.t.c