The attackers also abducted two sons and a daughter of police chief Col. Ali Dilayan al-Jorani, police said. The chief, head of central Baqouba's Balda police station, wasn't at home at the time, they said.
The children were described as young men and a young woman, but their ages weren't immediately available.
The two slain brothers were serving as guards at the house, in Kanaan town northwest of the city of Baqouba, which is 35 miles northeast of Baghdad.
The bodies of some guards, many of whom were also al-Jorani relatives, were found on a nearby road, apparently after being seized at the house, police said.
Diyala province, and particularly Baqouba, has been torn by violence in recent weeks as al Qaeda in Iraq and affiliated groups have battled Iraqi security forces, the U.S. military and some local insurgent groups that have turned against al Qaeda.
Later in the morning in southern Iraq, a parked minibus exploded at a bus terminal in the town of Qurna, and a hospital director said at least 16 people were killed and 32 wounded.
A witness, taxi driver Salim Abdul-Hussein, 35, said the blast damaged the terminal and many cars and surrounding shops, striking an area crowded each morning with farmers coming to town to shop and sell their produce and animals in Qurna, 225 miles south of Baghdad.
Maj. Gen. Mohammed Hammadi, police chief in Basra, the provincial capital 60 miles to the south, said a minibus loaded with rockets, ammunition, C4 explosive and benzene blew up and caused a nearby car to explode in flames — leading to an early report of two car bombs.
Police cordoned off the area and arrested two Egyptian suspects, he said.
Hammadi said eight people were killed and 28 wounded. Another police source, speaking on condition of anonymity because he was not authorized to deal with the press, said 15 people were killed. At Qurna hospital, director Ali Qassim told The Associated Press by telephone the hospital had received 16 bodies from the explosions and 32 wounded.
In other developments:
Meanwhile, Turkey's military command on Friday declared its "unshakable determination" to defeat Kurdish rebels, and a fourth soldier died of injuries from a bomb in a new Turkish security zone north of the Iraq border.
The roadside bomb, blamed on Kurdish separatists, exploded Thursday night and targeted a Turkish military vehicle near the city of Siirt, 45 miles north of Iraq, the governor's office said. In addition to the four dead, it wounded five other security personnel, the office said.
There has been increasing activity by Turkish troops along the frontier, which has fed concerns the army might stage a large-scale offensive against rebel bases in the predominantly Kurdish region of northern Iraq. The military on Wednesday announced new "temporary security zones" along the Iraq border during its campaign against the guerrillas.
Turkish leaders say the guerrillas cross into Turkey to stage attacks in their recently escalated fight to win autonomy for southeastern Turkey, where ethnic Kurds make up much of the population.
In a statement on its Web site, the military's general staff vowed to fight the rebels and called on all Turks to stand together "to resist in the face of these terrorist actions."
"The Turkish Armed Forces have an unshakable determination in fighting terrorism and it is a solid truth that it will give the necessary answer to such attacks," it said.