Chemistry means that we can share together. Best duty means that we have a duty to be responsible to perform what we have obligation. In this case, I assume you mean the two of us and family responsibility.
Chemical compatibility means we can live together. The obligation means we have a duty to act responsibly in practice what we have obligations. In here, I understand that you mean the two of us and family responsibilities.
Chemical compatibility means we can live together. The obligation means responsible for actions on treat what we have commitments. In here, I understand you mean us and family responsibility .