Royal biographer Andrew Morton gave a stark warning Prince Harry and William's feud could overshadow Philip's funeral.
The Duke of Edinburgh died aged 99 peacefully in his sleep with the Queen by his side at their home.
Only 30 members of the royal family will be able to gather to celebrate Prince Philip's life and say goodbye on Saturday amid the coronavirus pandemic.
Royal expert Andrew said all eyes around the world will be watching to see the reconciliation between William and Harry as well as Harry and his dad Charles.
A rift was torn in the royal family when Prince Harry joined his pregnant wife Meghan Markle for a tell-all chat with Oprah on TV.
Among a string of explosive claims, the Duchess of Sussex accused an unnamed member of the family to being racist about her unborn child.
During Steph’s Packed Lunch on Channel 4, the specialised biographer voiced his fears the attention on the ongoing feud and much-hoped for reunion could "undercut the tributes" to the late royal.
Asked about whether Philip's death would bring about a reunion, he said: “Everybody watching the funeral will want to see some sort of reconciliation between William and Harry, and Harry and his father…
"The one thing you hope is that it doesn’t overshadow tributes to Prince Philip. If everybody’s looking at what the lip readers are saying about the interaction between Harry and William, it will undercut the tributes to Prince Philip.”
He continued: “This isn’t the first time there’s been a Cain and Abel relationship inside the royal family, Elizabeth and Margaret were sort of the salt and pepper of the royals in their day.
"They were a unique double act and the comparisons with William and Harry are many and obvious. The Queen is a very similar character to William, cautious, even-handed and calm, Margaret and Harry are a couple who kick over the traitors. Margaret used to say, ‘disobedience is my job’.”
Fondly, Andrew remembered Prince Philip as "progressive" and the "head of the family".
He said: “Prince Philip was progressive, he was proactive as we all know, and he was a moderniser in a pretty crusty institution.”
He added: “His legacy was to bring the monarchy into the 21st century. He’s the one who, against the wishes of Winston Churchill and his wife, the Queen, got the coronation televised. He’s the one behind the royal family film of 1969. He was the head of the family, the head of the firm. His rule was law.”
Steph’s Packed Lunch airs weekdays at 12.30pm on Channel 4