Marconi was a friend of Charles van Raalte and his wife Florence, the owners of Brownsea Island; and of Margherita, their daughter, and in 1904 he met her friend, Beatrice O'Brien (1882–1976), a daughter of The 14th Baron Inchiquin.
 On 16 March 1905, Beatrice O'Brien and Marconi were married, and spent their honeymoon on Brownsea Island.
They had three daughters, Degna (1908–1998), Gioia (1916–1996), and Lucia (born and died 1906), and a son, Giulio, 2nd Marchese Marconi (1910–1971).
In 1913, the Marconis returned to Italy and became part of Rome society.
Beatrice served as a lady-in-waiting to Queen Elena.
At Marconi's request, his marriage to Beatrice was annulled on 27 April 1927, so he could remarry.
Marconi and Beatrice had divorced on 12 February 1924 in the free city of Fiume (Rijeka).

Marconi went on to marry Maria Cristina Bezzi-Scali (2 April 1900–15 July 1994), the only daughter of Francesco, Count Bezzi-Scali.
To do this he had to be confirmed in the Catholic faith and became a devout member of the Church.
He was baptised Catholic but had been brought up as a member of the Anglican Church.
On 12 June 1927 Marconi married Maria Cristina in a civil service, with a religious ceremony performed on 15 June.
 Marconi was 53 years old and his second wife, Maria Cristina Bezzi-Scali, was 26 years old, just under half her new husband's age.
 They had one daughter, Maria Elettra Elena Anna (born 1930), who married Prince Carlo Giovannelli (1942–2016) in 1966; they later divorced.
For unexplained reasons, Marconi left his entire fortune to his second wife and their only child, and nothing to the children of his first marriage.

Later in life, Marconi was an active Italian Fascist and an apologist for their ideology and actions such as the attack by Italian forces in Ethiopia.

In his lecture he stated: "I reclaim the honor of being the first fascist in the field of radiotelegraphy, the first who acknowledged the utility of joining the electric rays in a bundle, as Mussolini was the first in the political field who acknowledged the necessity of merging all the healthy energies of the country into a bundle, for the greater greatness of Italy".

Marconi wanted to personally introduce in 1931 the first radio broadcast of a Pope, Pius XI, and did announce at the microphone: "With the help of God, who places so many mysterious forces of nature at man's disposal, I have been able to prepare this instrument which will give to the faithful of the entire world the joy of listening to the voice of the Holy Father".
Marconi was a friend of Charles van Raalte and his wife Florence, the owners of Brownsea Island; and of Margherita, their daughter, and in 1904 he met her friend, Beatrice O'Brien (1882–1976), a daughter of The 14th Baron Inchiquin.  On 16 March 1905, Beatrice O'Brien and Marconi were married, and spent their honeymoon on Brownsea Island. They had three daughters, Degna (1908–1998), Gioia (1916–1996), and Lucia (born and died 1906), and a son, Giulio, 2nd Marchese Marconi (1910–1971). In 1913, the Marconis returned to Italy and became part of Rome society. Beatrice served as a lady-in-waiting to Queen Elena. At Marconi's request, his marriage to Beatrice was annulled on 27 April 1927, so he could remarry. Marconi and Beatrice had divorced on 12 February 1924 in the free city of Fiume (Rijeka).
Marconi went on to marry Maria Cristina Bezzi-Scali (2 April 1900–15 July 1994), the only daughter of Francesco, Count Bezzi-Scali. To do this he had to be confirmed in the Catholic faith and became a devout member of the Church. He was baptised Catholic but had been brought up as a member of the Anglican Church. On 12 June 1927 Marconi married Maria Cristina in a civil service, with a religious ceremony performed on 15 June.  Marconi was 53 years old and his second wife, Maria Cristina Bezzi-Scali, was 26 years old, just under half her new husband's age.  They had one daughter, Maria Elettra Elena Anna (born 1930), who married Prince Carlo Giovannelli (1942–2016) in 1966; they later divorced. For unexplained reasons, Marconi left his entire fortune to his second wife and their only child, and nothing to the children of his first marriage.
Later in life, Marconi was an active Italian Fascist and an apologist for their ideology and actions such as the attack by Italian forces in Ethiopia.
In his lecture he stated: "I reclaim the honor of being the first fascist in the field of radiotelegraphy, the first who acknowledged the utility of joining the electric rays in a bundle, as Mussolini was the first in the political field who acknowledged the necessity of merging all the healthy energies of the country into a bundle, for the greater greatness of Italy".
Marconi wanted to personally introduce in 1931 the first radio broadcast of a Pope, Pius XI, and did announce at the microphone: "With the help of God, who places so many mysterious forces of nature at man's disposal, I have been able to prepare this instrument which will give to the faithful of the entire world the joy of listening to the voice of the Holy Father".
Guglielmo Marconi