This is the Portsea baptism, but I would urge caution - check out everything you can before you accept that this is the right person.
John Bartlett, son of Richard & Sarah Bartlett, bapt 22 Jan 1788, St Mary, Portsea.
Possibly siblings (not allowing for spelling variants or that I might have missed some):
Henry Richard bp 9 Feb 1783 St Mary Portsea
Richard bp 30 Apr 1784 St Mary Portsea
Robert 13 Dec 1789 St John Portsea
Richard 31 Dec 1793 St John Portsea
Elizabeth bp 16 Aug 1795 St John Portsea
Nell