* EssiLux CEO Milleri named Delfin chairman

* Delfin's ownership divided equally among eight heirs

* Wife's son from previous marriage included in will

MILAN, July 4 (Reuters) - Leonardo del Vecchio's right-hand man on Monday took the reins of the 27 billion euro ($28 billion) holding company left behind by the Italian eyewear billionaire who died last week.

Del Vecchio's departure raised questions over the fate of some of his assets, in particular his stakes in financial firms Mediobanca and Generali, whose management the 87-year-old magnate had criticized.

Del Vecchio and fellow tycoon Francesco Gaetano Caltagirone in April lost out in a shareholder vote over leadership at Generali, while Mediobanca CEO Alberto Nagel's position comes up for renewal in late 2023.

Luxembourg-based holding company Delfin on Monday said it had named Del Vecchio's most trusted aide Francesco Milleri as chairman.

Milleri, 63, started as an IT consultant at Luxottica, the spectacle business Del Vecchio founded in 1961. Last year he became CEO of EssilorLuxottica after playing a key role in the negotiations that led to Luxottica's merger with French lens maker Essilor.

Following Del Vecchio's death, Milleri has also taken on the role of EssilorLuxottica's chairman.

Milleri's appointment at Delfin suggests there are no major changes in sight over Delfin's management of its assets, two people with knowledge of the matter said.

Unless they can bridge their differences, Milleri is expected to keep up the pressure on Nagel, a third person close to the matter added.

In a further sign of continuity, Delfin said its Chief Executive Romolo Bardin, another of Del Vecchio's longstanding associates, would continue in his role.

Shares in Mediobanca and Generali had suffered when Del Vecchio died due to market concerns that his heirs may cash in on the investments.

Del Vecchio had become in recent years the No.1 investor in Mediobanca with 19.4%. He was also the second-biggest shareholder in Italy's top insurer Generali, behind Mediobanca itself, with 9.8%.

He had considered further raising the Mediobanca stake before the European Central Bank made clear Delfin would have to subject itself to its oversight, a fourth person briefed on the matter said.

Del Vecchio has left his business empire to his six children, his wife Nicoletta Zampillo and her son from a previous marriage.

They now each own 12.5% of Delfin, whose main asset is the 32% stake in EssilorLuxottica, worth some 20 billion euros.

Based on Delfin's statutes, decision-making effectively requires unanimity because of the necessary 88.5% majority.

In addition to the stakes in EssilorLuxottica, Mediobanca and Generali, Delfin also owns 27% of Paris-listed Covivio and is a long-time investor in bank UniCredit with a 2% stake.

Zampillo, whom Del Vecchio remarried in 2010 after divorcing her a decade earlier, was originally expected to inherit Del Vecchio's 25% stake in Delfin.

The opening of Del Vecchio's will on Saturday showed that her son Rocco Basilico had received half of Del Vecchio's stake.

Basilico, 32, is head of wearable technologies at Luxottica.

As head of Luxottica's Californian brand Oliver Peoples, Basilico was instrumental in introducing Del Vecchio to Facebook founder Mark Zuckerberg.

The encounter led to the 2020 partnership between Facebook and EssilorLuxottica and the launch, in September 2021, of Ray-Ban Stories, smart glasses starting at $299 provided with a camera, speakers and microphones for calls and videos. ($1 = 0.9591 euros) (Additional reporting and writing by Valentina Za; Editing by Jane Merriman and David Evans)