According to the book “Naše gore list”, Volumes 2–3, published by Brzotis Ante Jakiča in 1862, Duke Mirko Petrović-Njegoš of Grahovo held a speech for Croats in Zagreb stating that Croats and Montenegrins were brothers, with one blood, one language and one name.

Cited:

“Duke Mirko to the Croats in Zagreb:

“I am pleased to hear, my beautiful Croats, that you speak and think so well of your Montenegrin brothers. That’s how it should be – we are one race, one blood, one language, one name!”

Full translation:

“[…] But even though the sun of freedom and glory of Montenegro has not darkened; from that sun, our Croatian faces have shone before God and before people. How happy and overjoyed we are that today we can deeply bow down to him and kiss his skirts, who led the Montenegrin knights to that glory. Long live the duke of all dukes, long live Mirko Petrovic!

Duke Mirko greeted him like this:

You have said, my beautiful Croats, what was on your heart. I am pleased to hear that you speak so and think so well of your Montenegrin brothers. That is how it should be: for we are one race, one blood, one language. one name, we have one Christian faith. Croats are good people and honest patriots. They have always had their great and famous dukes and heroes, and they would certainly be given

Duke Mirko to the Croats in Zagreb:

“I am pleased to hear, my beautiful Croats, that you speak and think so well of your Montenegrin brothers. That’s how it should be – we are one race, one blood, one language, one name!”

Source

Naše gore list, Volume 2–3. Brzotis Ante Jakiča, 1862. Indiana University.