Ichirō and some members of Hatoyama family are known as advocates of fraternity.
During the purge against Ichirō (1946–1951), he received an English book The Totalitarian State against Man originally written in German by an Austrian freemason Richard von Coudenhove-Kalergi from a professor of Waseda University Kesazō Ichimura (1898–1950) who wanted Ichirō to translate the English book into Japanese.
The English book struck a sympathetic chord in Ichirō, and he began to advocate fraternity, also known as yūai (友愛) in Japanese.

On March 29, 1951, he was initiated as 1st degree of freemason, and on March 26, 1955, passed as 2nd degree mason, and raised as 3rd degree mason.

His grandsons are advocates of fraternity.
However, when a Japanese press asked Yukio Hatoyama's office and the masonic grand lodge of Japan whether Yukio Hatoyama was a freemason, his office denied it and the grand lodge of Japan didn't answer it.
At least, on his grandson Kunio Hatoyama, the brother of Yukio, on a Japanese TV program Takajin no Money on August 25, 2012, his partner Emily's Australian father was a member of freemasonry.
He said so, and said he had swum in a masonic pool with her at Tokyo when he had started to going steady with her.
 Although he didn't say he himself was a mason or not, he insisted that he had not been invited to freemasonry, and he guessed his brother Yukio as a freemason.

Yukio and Kunio became the officers of a fraternal organization named Yūai Kyōkai (or Yūai Association) with their sister Kazuko, founded by their grandfather Ichirō who became the first president of the former organization in 1953.
And also Ichirō's son Iichirō became the third president of the same former organization.

The granddaughter and two grandsons of Ichiro's founded a fraternal school Hatoyama Yuai-Jyuku at Hatoyama Hall (Hatoyama kaikan) on April 2008.
Ichirō and some members of Hatoyama family are known as advocates of fraternity. During the purge against Ichirō (1946–1951), he received an English book The Totalitarian State against Man originally written in German by an Austrian freemason Richard von Coudenhove-Kalergi from a professor of Waseda University Kesazō Ichimura (1898–1950) who wanted Ichirō to translate the English book into Japanese. The English book struck a sympathetic chord in Ichirō, and he began to advocate fraternity, also known as yūai (友愛) in Japanese.
On March 29, 1951, he was initiated as 1st degree of freemason, and on March 26, 1955, passed as 2nd degree mason, and raised as 3rd degree mason.
His grandsons are advocates of fraternity. However, when a Japanese press asked Yukio Hatoyama's office and the masonic grand lodge of Japan whether Yukio Hatoyama was a freemason, his office denied it and the grand lodge of Japan didn't answer it. At least, on his grandson Kunio Hatoyama, the brother of Yukio, on a Japanese TV program Takajin no Money on August 25, 2012, his partner Emily's Australian father was a member of freemasonry. He said so, and said he had swum in a masonic pool with her at Tokyo when he had started to going steady with her.  Although he didn't say he himself was a mason or not, he insisted that he had not been invited to freemasonry, and he guessed his brother Yukio as a freemason.
Yukio and Kunio became the officers of a fraternal organization named Yūai Kyōkai (or Yūai Association) with their sister Kazuko, founded by their grandfather Ichirō who became the first president of the former organization in 1953. And also Ichirō's son Iichirō became the third president of the same former organization.
The granddaughter and two grandsons of Ichiro's founded a fraternal school Hatoyama Yuai-Jyuku at Hatoyama Hall (Hatoyama kaikan) on April 2008.
Ichirō Hatoyama