Was the city’s absurdly generous payment for a pack of Bronx and Brooklyn properties just a payback for a personal favor to Mayor Bill de Blasio? New facts confirm that an independent investigation is needed.

Months ago, Comptroller Scott Stringer flagged the $173 million purchase of 17 buildings from brothers Jay and Stuart Podolsky, since one city appraisal valued the properties as low as $49.7 million. But City Hall blew off Stringer’s request for a full accounting.

Now the Daily News reports that de Blasio got mortgages on his two Park Slope properties from a bank founded by another Podolsky brother, a bank Brooklyn Democratic Party counsel Frank Carone also once worked for. The bank also once shared an address with the law firm where Carone and Brooklyn party boss Frank Seddio were partners.

The mayor’s defenders claim older brother Abraham has been estranged from his siblings for years. Other sources say the Podolskys since reconciled.

Carone was Jay and Stuart Podolsky’s attorney during negotiations for the $173 million purchase. He gave the maximum $5,000 to de Blasio’s Fairness PAC at that time, and has since held a fundraiser for the PAC.

City Hall claims a Stringer review of the appraisals “would interfere with the City’s future negotiations for property acquisitions.” Hmm: If the info’s too confidential to share with the comptroller, then a prosecutor should probably look into it.