"Harmonious relations" refers to having positive and peaceful interactions with others, where everyone gets along and cooperates well together. Full definition
He linked this to their role in fostering industrial peace and harmonious relations between management and unions. (erudit.org)
This is quite compatible with the needs of the economic and political order for harmonious relations among cultural groups. (religion-online.org)
The two territories have enjoyed harmonious relations through their history and have shared the prosperity of many years without dispute. (havebabywilltravel.com)