common ground
US /ˈkɑː.mən ˌɡraʊnd/
UK /ˈkɑː.mən ˌɡraʊnd/

1.
shared interests, beliefs, or opinions between two or more people or groups
:
•
Despite their differences, they found common ground on the issue of education.
•
It's important to seek common ground when negotiating.