Jonathan Pamphilj and Gesine Doria are understood no longer to be on speaking terms
By David Willey
BBC News, Rome
Two British orphans adopted by one of Rome's most famous princely papal families are locked in a bitter legal feud over which of their children will eventually inherit an estate reportedly worth more than 1bn euros (£930m).
At the heart of the row is whether the children of one of the orphans - who is gay and had his offspring via a surrogate mother - have a legal right to the family fortune.
The estate includes a 1,000-room palace in Rome, another in the centre of Genoa, plus one of the world's most valuable art collections.
The two grown-up orphans, Jonathan and Gesine Doria Pamphilj, frequently style themselves as Prince and Princess, although all former royal and papal titles were formally abolished in Italy when the country became a republic after World War II.
I know them both well as, until last spring, I was one of 250 tenants in their sprawling 16th-Century palace.
I understand they are no longer on speaking terms because of the inheritance dispute.
Frank Pogson and Princess Orietta Doria brought their children up in luxury after plucking them from a British orphanage in the 1960s
Gesine prefers to be called Donna Gesine, a courtesy title recalling her family's long history (there was a Doria Pope - Innocent X - in the 17th Century while Andrea Doria, the famous Genoese admiral, was from another generation).
She is married to a commoner, Massimiliano Floridi, by whom she has four daughters, the eldest of whom is now 15 and the youngest five.
Massimiliano, an art expert, is a devout Catholic and was recently inducted into the church as a deacon by his local bishop.
Jonathan was brought up as Gesine's brother, although they are biologically unrelated. He was educated at Downside, the English Catholic public school.
He is in a British-registered civil partnership with a gay Brazilian man, Elson Edeno Braga, and has two children born of foreign surrogate mothers, aged three and two.
The problem is that, according to Gesine, a recently passed Italian law on assisted procreation means that Jonathan's two children may have no rights of inheritance to the family fortune.
Same-sex marriages are not recognised in Italy, which is why he chose to register a civil partnership in the UK.
Gesine told me that she began a legal action in Rome two years ago to establish the paternity of one of Jonathan's two children.
News of this leaked out in the Italian press last weekend, and has now been published abroad as well.
Jonathan is not answering calls and has issued a brief statement refusing to comment on his sister's legal action in the interests of his children.
Gesine told me: "I advised Jonathan to adopt children, just like our parents did, but he refused because he wanted his own children by surrogate mothers.
"He failed to realise that, under current Italian law, if you are a sperm donor, you cannot claim parentage. Only the mother who actually gives birth to a child has the right - and the obligation - to look after that child.
"I wanted to clear things up for the future because sooner or later when we die this situation will explode. We don't know what the future is.
David Willey used to be one of the 250 tenants at the Doria Pamphilj palace
"I am taking this action as much for the benefit of Jonathan's children as for my own, and I am not expecting a rapid decision by the Rome judge."
Gesine chose to bring up her own family in a country house in the mountains south of Rome, not in the imposing Doria Pamphilj palace, where she retains a suite of rooms but only comes to visit at weekends.
Jonathan, on the other hand, lives in the palace in his own apartment and administers the family's real estate from an office in another part of the palace complex which occupies a whole city block.
Jonathan and Gesine's adoptive father was Frank Pogson, a British naval frigate commander who met Princess Orietta Doria during WWII.
By the time they married, Princess Orietta and Don Frank, as he was known, were unable to have children of their own and decided to adopt instead.
But it meant that, when she died in 2000, the blood line of the family was extinguished.
The family art collection is open to the public and Jonathan's voice accompanies visitors on an audio guide.
The collection includes works by Caravaggio, Titian and Giorgione and the famous portrait of the Doria Pope, Innocent X ,which Velasquez painted in this palace and which is given pride of place with a small room to itself.