How do “sister cities” find each other and agree to be sisters?

Question

How do “sister cities” find each other and agree to be sisters?

In: 5760

Answer 1

Paris and Rome are twin cities since 1956 and mutually decided not to sign any other agreement while major world capitals are often with several cities (NYC has 13 twin cities). The motto of the twinning between the two cities is “Only Paris is worthy of Rome; only Rome is worthy of Paris.”