Answer:
reciprocity
Explanation:
We can say that their relationship has a high level of reciprocity. In other words a give and take. They each help each other out, and do things for one another, while also helping the other with the their tasks when they need the help. This demonstrates lots of trust, love, and respect for one another which is why they are always there for each other. This is all part of reciprocity in a relationship, which is why we can say that they have a high level of it.