The four women, one man and six children were caught "after weeks of 24/7 surveillance," he said. Among them was a woman who was later identified to be Asma Fawzi Muhammad al-Qubaysi, al-Baghdadi's first wife, the official added.
Another detainee, who identified herself as Leila Jabeer, was determined to be al-Baghdadi's daughter following a DNA test, the official said, citing a police report.
He also said that al-Baghdadi's DNA sample was provided by the Iraqi government.
Al-Baghdadi - proclaimed the caliph, or leader, of Islamic State in 2014 - died on October 26 in Barisha, in the north-western Syrian province of Idlib, near the Turkish border.
The detainees from Hatay are currently being held at a deportation centre inside Turkey, the official told dpa.
Criticizing the United States for launching "a very solid communication campaign" about al-Baghdadi's death, Erdogan said during a speech in Ankara: "We captured his wife. But, we did not make a fuss out of it. I announce it for the first time today."
The Turkish official wouldn't say why the information was not disclosed earlier.
"We discovered her real identity pretty quickly," he claimed of al-Baghdadi's wife.
"At that point, she volunteered a lot of information about [al]-Baghdadi and the inner workings of ISIS," he said, adding that this led to several arrests elsewhere.
"There may or may not be other high-value targets in Turkish custody. I am not at liberty to discuss ongoing investigations and intelligence operations," he added.
On Tuesday, Turkey said it had captured al-Baghdadi's sister Rasmiya Awad during a raid in Azaz, a Syrian town controlled by Turkish-backed rebels, as well her husband, daughter-in-law and five children.
Erdogan confirmed on Wednesday that al-Baghdadi's sister and brother-in-law were taken into custody "on the Syrian side."
Awad, 65, and her family had been living in the camp of container housing units for a year, according to Rami Abdel Rahman, head of the Syrian Observatory for Human Rights, a war monitor.
But Abdel Rahman raised questions about the timing of the arrests' announcements.
"The Turkish intelligence service was aware of her presence in the area [before capturing her]," Abdel Rahman said.
Hundreds of Islamic State members and their families remain in Turkish-controlled areas in northern Syria. "I expect in the coming weeks that Turkey will detain more [Islamic State] members in order to show it is active in the fight against terrorism," Abdel Rahman told dpa.
Turkey launched its incursion into north-eastern Syria on October 9 with a stated aim of fighting Islamic State and Syrian Kurdish militias it considers terrorists.
The Turkish military and its allied Syrian rebel groups took control of Azaz following Operation Euphrates Shield in 2016, Turkey's first incursion into northern Syria.
Azaz, in the Syrian province of Aleppo, lies 14 kilometres from the Turkish border. It is 80 kilometres away from Barisha, where al-Baghdadi was hiding out and eventually died.
US President Donald Trump announced al-Baghdadi's death on October 27, saying he blew himself up after he was trapped by US special forces in a tunnel within a compound in Barisha.
Trump and Erdogan will meet on November 13, both leaders confirmed after a phone call on Wednesday.
Trump also tweeted that Erdogan "informed me that they have captured numerous ISIS fighters that were reported to have escaped during the conflict – including a wife and sister of terrorist killer al Baghdadi."
The 48-year-old al-Baghdadi was reclusive and secretive. His only known public appearance was a sermon in July 2014 at a mosque in Mosul just after Islamic State captured the northern Iraqi city and declared its caliphate.
There are more rumours than concrete information about his family. The New York Times reported that al-Baghdadi had five brothers and several sisters, and was believed to have four wives, but couldn't confirm how many of them were alive.
One of al-Baghdadi's sons, Hudhayfah, was killed in 2018 in a suicide bombing in the Syrian city of Homs, the group announced at the time. He was believed to be 13.
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