This is an account of one large family, 15 children and their parents, who all left Sussex at different times seeking a better life abroad. A search on Ancestry for Thomas Boots senior results in over 600 trees so this is a well researched family but I wanted to bring together their individual stories as part of my research into the emigration from the Kent / Sussex borders of my wider family in the 19th century. The 'mother' of this family, Hannah Tree, is a distant aunt of mine.
In 1800 Hannah Tree married Thomas Boots in Ewhurst, Sussex. Hannah was around 19 years old at the time having been baptised in the village in 1781 and Thomas was about two years older.
In next 26 years, between 1800 - 1826, they had 15 children all who survived to adulthood.
1823 - son Henry emigrates to America: the first to leave
In 1820 their second son, Henry Boots who had been baptised in Northiam on 31 January 1802 married Ann Dearing in Salehurst. Less than two years later, on 4 July 1823, Henry and Ann arrived in New York on the Hudson with their 1 year old daughter Mary Ann. 
1828 - parents Thomas and Hannah follow Henry to America
In 1828 Henry’s parents Thomas & Hannah Boots joined him in America, sailing on the Electra which arrived in New York on 7 July . The passenger list shows their 7 youngest children travelling with them: Joseph 17 (age shown as 19), William 15, Ann (Jane) 13, Martha 10, John 6, Daniel 4 and George 2. Not on the list are 17 year old Sophia / Sophy or 11 year old Benjamin although both did make it to America and I can find no evidence of them remaining in England or of them travelling separately to their parents.
On arrival Thomas Boots senior and his family travelled to Hastings, Oswego County in the State of New York . In the 1830 census their son Henry was living in Onodaga in the same general area, south of Lake Ontario.
Four months after arriving in America, on 29 November 1828, Hannah gave birth to their last child Robert Freeborn Boots.
On 2 December Thomas wrote a letter to his son James in England about their new life in America and apart from a few drawbacks, such as the state of the roads and the distance from the stores, overall it is a positive account . Within a short time of arriving Thomas had bought 12 1/2 acres of land and two cows and had also built a framed house. In the letter Thomas refers to Hannah recovering from the birth of the baby [Robert]. He also says Henry, his wife and two children [Mary Ann born in England and Henry jnr born 1825 in America] are doing well although a third child, a son, had recently died aged 7 months.
Thomas and Hannah do not seem to appear in the 1830 census, although Henry is listed and by then had another son [Marcus born 1829].
When Thomas and Hannah emigrated they left behind five adult children in Sussex: Thomas 28, Hannah 25, James 23, Mary 22 and Sarah 20 and in his letter Thomas senior encourages them to consider emigrating. He tells them whose help to enlist and what to bring with them.
1830 - daughters Hannah & Sarah emigrate to America
Perhaps spurred on by the positive letter and reports from other emigrants, on 7 July 1830 sisters Hannah and Sarah arrived in New York on the Brig Sussex . With Hannah was her husband John Saunter and 4 year old daughter also called Hannah. With Sarah was her husband William Barnes and 2 year old son James. The two sisters and their families are listed next to each other in the passenger list.
This left three children still living in England and despite the encouragement of their parents to emigrate it was to be another 10 years before any further emigration took place, and then to Australia not America.
1838 - daughter Mary emigrates to Australia
On 6 Nov 1838 Mary, then aged 32, and her husband George Waters (Wattus) a ploughman arrived in Sydney with their 5 young daughters aged between 3 and 10 having travelled on the Maitland.  Mary, who had several more children in Australia died nine years later possibly as a result of childbirth.
1839 - son James emigrates to Australia
Eleven months later, on 27 Sept 1839, James arrived in Sydney on the Neptune with his wife Sarah Ann nee Clapson and their 4 year old son John. 
Why did these two siblings decide to go to Australia rather than join the rest of the family in America? There was certainly a lot of emigration at this time from the area to Australia. Their uncle Daniel Tree from Northiam was another of the many emigrants, arriving in South Australia in January 1839 on the Resource. 
Whatever the reason, after they left their oldest brother Thomas was, for the next ten years, the only one of the 15 children in England
1849 - son Thomas emigrates to America
In 1849 the eldest son Thomas then aged 48 and his wife Mary 46 finally made the journey to America with three of their children: Thomas 19, George 16 and Sofia 9. They departed London for Montreal on 9 May on the Oriental and then made the journey across the border to join the family in New York State. 
Afterwards in America
In the 1840 census the two sisters, Hannah (Saunter) and Sarah (Barnes) who had travelled together to America in 1830 were living with their husbands and families at Constantia on the north shore of Oneida Lake. The Barnes family remained there but by 1850 the Saunters had moved to Michigan.
In the census recorded on 10 August 1850 Thomas junior and family were living in Constantia next door to his brother Benjamin and family but by the time the enumerators had made it to Cicero on 2 November 1850, Benjamin had moved there so was recorded twice in that year's census.
Within a few years of arriving in 1849 both of the sons of Thomas junior had married: Thomas junior 2 (as he was described in the 1855 census) married Mariah from St Lawrence and George’s wife Sarah came from Oswego.
By 1855 Thomas Boots senior and Hannah his wife, the couple whose story I began with, where living in West Monroe, Oswego with son Thomas junior and his family. The next two households listed are those of their grandsons (Thomas junior's sons), Thomas junior 2 and George with their wives and children (the great grandchildren of Thomas and Hannah).
What of Thomas and Hannah's other children? I have carried out little research on those who sailed to America with their parents but it would appear from Ancestry that William died in Oswego in 1832 aged 18 and Josiah, Martha and George continued to live in New York State together with their American born brother Robert (who enlisted in the 110th Infantry to fight in the Civil War). Sophy and Ann / Jane both married and moved to Michigan and John and Daniel to Iowa.
And in Australia..
James and his family settled in Raymond’s Terrace, New South Wales as did Mary with her husband George Waters / Wattus and their family until her death in 1847.
Notes New York, Passenger and Crew Lists (including Castle Garden and Ellis Island), 1820-1957 Year: 1823; Arrival: New York, New York, USA; Microfilm Serial: M237, 1820-1897; Line: 26; List Number: 446  New York, Passenger and Crew Lists (including Castle Garden and Ellis Island), 1820-1957 Year: 1828; Arrival: New York, New York, USA; Microfilm Serial: M237, 1820-1897; Line: 19; List Number: 357  The emigrant's guide; in ten letters, addressed to the tax-payers of England; containing information of every kind, necessary to persons who are about to emigrate; including several authentic and most interesting letters from English emigrants now in America, to their relations in England; and an account of the prices of house and land, recently obtained from America by Mr. Cobbett. | Library of Congress (loc.gov)  Ancestry.com. New York, U.S., Arriving Passenger and Crew Lists (including Castle Garden and Ellis Island), 1820-1957 Year: 1830; Arrival: New York, New York, USA; Microfilm Serial: M237, 1820-1897; Line: 39; List Number: 334  Ancestry.com. New South Wales, Australia, Assisted Immigrant Passenger Lists, 1828-1896 [database on-line]. Provo, UT, USA: Ancestry.com Operations Inc, 2007.  Ancestry.com. New South Wales, Australia, Assisted Immigrant Passenger Lists, 1828-1896 [database on-line]. Provo, UT, USA: Ancestry.com Operations Inc, 2007.  https://collections.slsa.sa.gov.au/resource/B+47769/page:12  SFHG Journal vol 3 issue 6 September 1978 / Salehurst Parish Records