The first son Martin, was a child of Major Mountjoy Martyn who was already married. His baptism at Holy Trinity Marylebone, was 27 Sept 1842 and birth date stated at that baptism was 16 Aug 1842. The nearest equivalent was a Martin Mountjoy born in the Strand in 1839, but I am sure the vicar could destinguish a month old child to one aged 3 years. Martin and his mother joined Napoleon III in France prior to 1851 and he grew up there to become Martin Constantine Haryett, the Earl of Bechevet.
Even though his grandparents (Joseph & Elizabeth Haryett of Brighton) lived in Suffolk and had their last child 20 years earlier, a second child, William Alderton Haryett was still baptised as their son in Brighton in 1847. William also had no known birth registration and like his grandparents, fails to appear on the 1851 census. I would like to say the grandparents and William also moved to France to join their daughter in her Chateau in Versailles, but as the 1861 census verifies, the grandfather remained a decorator, listed as Joseph Hargett of Brighton and wife Elizabeth living at High Street (Road?) Mutford, Gorleston, Suffolk. RG9/1189/140. The grandfather came into wealth after his daughter's death in 1865, returning to Brighton where he reappeared not as a tradesman, but listed amongst the town's gentry.
Roy G