Mr Sidney Conrad Siebert was born in Battersea, London, England on 23 September 1882.

He was the son of Conrad Siebert (1861-1948) and Ann Amelia Brown (1861-1925), natives of Whitechapel, London and Brightlingsea, Essex who had married on 26 December 1881. His father, a chair maker, was the son of an English mother and a German father. Sidney had only one known sibling, his younger brother Marcus William (1884-1955). Through his parents' secondary marriages he had one half-sister and five half-brothers.

Sidney's parents later separated but it is not clear if they were ever divorced. His father remarried, seemingly committing polygamy, in 1887 to Emma Scudamore (b. 1885) from London and had three children: Emma Elizabeth (b. 1889), Conrad Joseph (b. 1892) and Steven Ernest (b. 1897). The family lived at 14 Lidyard Road, Highgate, north London by the time of the 1911 census.

Sidney first appears on the 1891 census and at this time he is living with his mother and brother William at an address in Brightlingsea, Essex, the home address of a maternal great-aunt, Eliza Ganter; his mother then described herself as a widow. Sidney and his brother are with the same great aunt in the 1901 census - this time at 22 Nelson Street, Brightlingsea - and Sidney is listed as unmarried and described as a "yacht block maker".

His mother had remarried in 1892 to Edwin Arthur Perry (b. 1861), an Essex-born marine engineer, and the couple had three children: Arthur Edwin (b. 1893), Percy Thomas (b. 1895) and Clement Charles (b. 1898). That family were living at 97 Eton Road in Ilford, Essex by the time of the 1911 census.

Sidney was married on 5 October 1907 to Winifred Rose Savage (b. 16 December 1883), a Brightlingsea-native. The couple moved to Southampton sometime prior to 1909 where and when their first born child, Winifred Ena was born. The child survived only a few weeks. A second child would be born on 8 December 1910, Lilian Elsie.

On the 1911 census Sidney is absent but his wife and daughter are shown residing at 33 Church Street, Shirley, Southampton.

Siebert was part of the skeleton delivery crew on Titanic to see the ship from Belfast to Southampton. Whilst in Belfast to wrote to his wife from the central library, expressing his distaste for the city and lamenting on the Irish weather:

“My dear Darling Winnie

“I have bought a little note paper so that I could drop you a few more lines than I could get on a postcard.

“As I told you we had a very trying journey here... we were over 11 hours in the train and then straight on to the steamboat for another eight hours and nowhere to sleep all that time and she was a rather old boat we came over by.

I hope you are still keeping well. I am glad to say I am alright... the air here is very bracing it makes me as hungry as anything.

I don’t think a great deal of the City it is not so good as Soton although there are several fine buildings here, but the town itself is very dirty and it has been raining ever since we got here.

I am writing this in the Public Library, a very nice building but not up to date English books and papers seem very scarce here.

Also another thing which strikes one as curious is that there are no cabs or taxis here they all have these jaunting cars as sort of a shelf arrangement on two wheels and they look most decidedly uncomfortable.

I have not tried one yet and have no intention of doing so.

I expect we are leaving here for our trials on Monday and for home on Tuesday and I can tell you I shall be glad after that long time at home I don’t like being away at all.

But I suppose I must not grumble as I have had a good time while I was home and must not get on and earn some money.

Kiss baby for me tell her her daddy wants to see her and I want to see my other little girl as well.

Good Night my own beloved with all the hearts love...”

When Sidney signed on to the Titanic in Southampton for the maiden voyage he gave his address as 8 Harold Road, Southampton, the same address given by his brother-in-law Charles Savage who was also serving aboard. His previous ship had been the Oceanic and as a bedroom steward he would earn £3, 15s per month.

On the night of the disaster Sidney Siebert reportedly jumped overboard with fellow-steward Andrew Cunningham and was picked out of the water and into lifeboat 4. Siebert did not last the night. If he was among the swimmers plucked into boat 4, his body may have been buried at sea. His brother-in-law Charles Savage was among the saved.

There is a memorial tile to Siebert at the All Saints Church in Brightlingsea, Essex.

Siebert's widow Winifred, who was pregnant at the time of the disaster, later returned to her native Essex and gave birth to a daughter named Constance Winifred on 18 November 1912. She never remarried and died in Solihull, Warwickshire in 1966.

His daughter Lilian was married in Southampton in 1930 to Frederick James Browne (1907-1993) and moved to Somerset. She died in 1989.

His daughter Constance was married in Southampton in 1936 to Percival H. Jones and she died in Winchester in 2003.