The Bee Gees singer died of cancer in May. He was 62.
The Sun newspaper in London said it might take five years to divide up Gibb's assets since some of his money is tied up in international businesses and properties.
His estate is expected to be divided among his wife, Dwina, and children -- Melissa, Spencer and R.J., the newspaper said.
Claire Yang, a housekeeper with whom Gibb had a 3-year-old daughter, reportedly received an $8 million settlement and a house before his death.
"Probate could take years to sort out. No one but Claire's received anything so far," a friend of the Gibb family told The Sun.