Hello Sid.. welcome to the forum
Are you wanting to find out about his family in Argentina or his roots in Liverpool?
You may already have all this, but here is some info to go on with
Sidney's baptism is on Ancestry, baptised 29/5/184 at Everton, St George, to Alfred and Jane Plant. Alfred was a Brass Founder and they were living at Northumberland Terrace.
Their marriage also looks to be there although Alfred's occupation somewhat different
Everton, St George
Jane Beaver, 10 Osborne Grove
Birth Year: abt 1842
Age:19
Marriage Date: 27 Jan 1861
Parish: Everton St George
Spouse's Name: Alfred Plant, Merchant, 27 Conway Street
Father's Name: Jonas Beaver, Iron?
Spouse Father's Name: Joseph Plant , Tailor
1871 census
RG10; Piece: 3818; Folio: 19; Page: 31
38 Monk Street
Alfred Plant 32 Brassfounder, b ? Staffordshire
Jane Plant 29 B Liverpool
Thomas A Plant 9 b Liverpool
Sydney H Plant 7 b Liverpool
James T Plant 2b Liverpool
Edith G Plant 4 Months b Liverpool
1881
RG11; Piece: 3670; Folio: 43; Page: 17
22 Burleigh Road South
Alfred Plant 42 Book keeper,Engineer & Iron Founder, b Lichfield Staffordshire
Jane Plant 39 b Liverpool
Thomas A. Plant 19 Brass Finisher
Sydney H. Plant 17 Iron Moulder
James W. Plant 12 scholar
Edith I. Plant 10
Gertrude M. Plant 8
Lily M. Plant 5
Clara Plant 3
Frederick P. Plant 11 months
Simone x