Kunio Hatoyama’s resignation Friday as internal affairs and communications minister has fueled speculation he could join his brother Yukio, leader of the main opposition party, in a two-pronged family attack on Prime Minister Taro Aso, the grandson of their grandfather’s archrival.

The minister quit his Cabinet post after the recent kerfuffle over the management of Japan Post Holdings Co., a symbol of Japan’s postal privatization reforms.

After tendering his resignation to Aso, Kunio, who has been a close ally of the prime minister, told reporters, “I will consult with my fellows” on whether or not he will leave the Liberal Democratic Party. On Saturday in Fukuoka, he said he does not plan to leave the LDP at the moment.

Yet, he criticized Aso in a separate speech the same day, saying “Prime Minister Aso can’t take the leadership, and his government is in terminal condition.”

The two brothers, grandsons of former Prime Minister Ichiro Hatoyama, have recently been rumored to be seeking to tie up and form a new party ahead of or shortly after the coming election for the House of Representatives, which must be held within the next few months.

Despite Kunio’s remarks, some political analysts do not rule out the possibility of the two joining hands in the future.

“His resignation has cleared the way for the next step (a possible alliance) in a very good way,” said Eiken Itagaki, a political analyst who has written a series of books on the brothers, their grandfather and father Iichiro Hatoyama, a former foreign minister.

“If the DPJ secures a majority in the election, Kunio would have a good chance of getting a key post,” Itagaki said, adding that he has ambitions to become prime minister.

Analysts believe the DPJ has a good shot at wresting power from the ruling LDP-New Komeito bloc at the next general election, given the problems Aso faces and his low popularity.

When the Japan Post issue was deepening last week, Yukio, who has charged Aso with wasteful economic measures and bureaucracy-oriented policymaking, invited Kunio to leave the post quickly and “take a new road.”

“In the political circles of Nagata-cho,” Yukio said, “two pigeons are poking at Prime Minister Aso. I am doing it fair and square, but the other is gouging out his insides,” referring to Kunio. The word “hato” means pigeon.

Aso had been in a dilemma for several weeks, as Kunio insisted that Yoshifumi Nishikawa be removed as head of the government-owned Japan Post, while reformists and many other lawmakers in the LDP said Nishikawa should stay and press ahead with the reforms.

Signaling their increasing closeness, the Hatoyama brothers formed a political school last year called Hatoyama Yuai Juku (Hatoyama Fraternity School) to promote a philosophy of fraternity as advocated by their grandfather, with the aim of creating a society based on love and happiness.

In addressing students of the school in April 2008, Yukio said, “People say we are at strife, but I have never forgotten the bond called ‘love’ (with my brother) and would like you to learn the various forms of the fraternal spirit.”

Itagaki said it doesn’t matter to them whether or not they belong to the LDP or DPJ.

“They are seeking to join hands over something greater, and that is fraternity,” Itagaki said.

At a party last December, Kunio also said that which political party they belong to was decided in “almost the same way as when we are separated by lottery into a ‘red’ or ‘white’ group (at sports events) in elementary school.”

“It is desirable that a party be formed by those who have the same ideas, philosophies and basic policies,” he added.

He has also played up his intimacy with Yukio.

“The relationship between my brother and me is closer than that between my brother and (then) DPJ President Ichiro Ozawa. My brother is always saying that too,” he said.

Listening to Yukio’s fraternity philosophy, Aso, grandson of former Prime Minister Shigeru Yoshida, retorted in their first Diet debate in late May that Yukio is merely calling for a change of government and failed to present specific ideas or policies of his own.

The grandfathers of Aso and the Hatoyama brothers were political foes in the immediate postwar period.

Yukio and Kunio used to belong to the LDP. Both left the party in 1993 and later formed the DPJ together, but Kunio left the DPJ in 1999 to run unsuccessfully in the Tokyo gubernatorial election. The brothers also failed to form a consensus on the party’s policies.

Since Kunio rejoined the LDP in 2000, the brothers have often been at loggerheads. Kunio has been close to Aso and had taken the lead in campaigning for him in the LDP leadership election.

The two brothers have become closer than before, but Kunio can sometimes be harsh toward his brother. After the Diet debate, he said Yukio was just a “puppet” of Ozawa, his influential predecessor.