It’s all in the family.

Two brothers of Yonkers Mayor Mike Spano run a lobbying firm with 23 clients that have had business before the Westchester County city during the mayor’s tenure — including with the agency that doles out tax breaks and is chaired by him, records show.

Empire Strategic Planning was founded by Nick Spano, a former Republican state senator and Mike’s older brother who was convicted of a tax crime in 2012.

John Spano, another brother, is on ESP’s executive team.

Twenty-three of the lobbying firm’s 47 clients currently have or have had business before the Yonkers government or its industrial development agency, which is chaired by Mayor Spano, since he took office.

The firms pay EPS about $65,000 combined per month, according to state lobbying records.

A former partner of the firm is Jim Cavanaugh, who is now president and CEO of the Yonkers IDA.

Meanwhile, there are at least 14 Spano relatives on the city municipal payroll totaling $2 million, Lohud.com reported last month.

While the 23 firms have business before the city, both Mayor Spano and his siblings-led firm recently told The Post that his brothers lobby on these clients’ behalf before the statehouse in Albany — not Yonkers’ City Hall.

None of the firm’s clients has been accused of any wrong-doing.

But Spano’s mayoral opponents and other Yonkers insiders say even an appearance of a potential conflict of interest is enough to warrant questions.

“This is an abuse of power and yet another example of how Mike Spano uses his position as mayor to enrich his friends and family at the expense of the people,” claimed Yonkers Councilman Corazon Pineda Isaac, who is challenging Spano in the Democratic primary as he seeks a fourth term.

“The people of this city deserve better. Yonkers needs a change,” Pineda said.

Anthony Merante, the Republican candidate for mayor, said that if the mayor or any elected official profited from their public service, “That would be a serious violation of the public trust.”

Among the clients who the Spano brothers’ ESP firm represents are:

The IDA’s Cavanaugh did not immediately return a phone message from The Post seeking comment Sunday.

John Kaehny, executive director of the government watchdog group Reinvent Albany, said, “There’s a lot of smoke coming from Yonkers.

“The question state investigators should answer is whether there is a corruption fire.”

Kaehny said the state Authorities Budget Office should determine if the Yonkers IDA is giving “preferential treatment” by doling out public funds for tax breaks to the ESP clients. The IDA’s duties include offering state and local tax exemptions and property-tax abatement, according to its website.

The state commission on ethics and lobbying in government should see if ethics and lobbying laws are followed, too, Kaehny said.

Mayor Mike Spano’s office insisted there’s nothing to look at.

“Empire State Planning does not lobby the City or the IDA, per the request of Mayor Spano at the start of his administration. All of those clients have business before the State or other municipalities, not Yonkers,” said the mayor’s spokeswoman, Christina Gilmartin, in a statement.

Maureen Kronau, an ESP executive who works with the Spanos, said, ” ESP does not lobby Yonkers, even though the law would allow us to.

“We represented many of the clients before Mike Spano even ran for Mayor, and in all cases we are hired to represent them in matters involving state government or other municipalities,” she said in a statement. “That’s made clear in every lobbying contract.”

Kronau specifically cited some of its clients who pre-existed Mike Spano’s mayoralty — including the O’Connor Davies accounting firm, Empress Emergency Medical Services and St. Joseph’s hospital.

One Yonkers political insider questioned the need for firms or unions to hire the Spano firm because the most powerful Democrat in the state Senate — Majority Leader Andrea Stewart Cousins — represents Yonkers and could look after interests there.

“If I want something done in Albany, I’m going to Andrea Stewart Cousins. It isn’t about getting things done in Albany,” claimed the source, who requested anonymity.

“You want to be looked at favorably in Yonkers, you hire the Spano lobbying firm.”