Hi Graham
Sorry for the late reply
I did mention previously that your John could be a potential brother to my Harriet. The names of the children are similar, and both John and Harriet ended their days by working/living in pubs (John in the Curriers Arms, Harriet in the Horse & Groom)
Unfortunately, I still have not been able to find a link between the two or find suitable baptism entries in the Stepney area. There are other Malden's in the Stepney area around the 1750-1770's and at least one known family in nearby Limehouse in the early 1820's
As for William, I have more information. There is another version of his service record which reveals he was born in the parish of Logie Buchan, Aberdeenshire in 1796. He was the son of John Stephens. He also appears to have an elder sister, Ann, who was also born in Logie Buchan in 1791.
William's service record revealed that his service in India began on 28 June 1817. If the regiment was already in India on that date, then it could mean Harriet ran away with William when she was ~14 years old.
Other possibilities could be the Malden's were on-board with the regiment when they sailed for India (perhaps William and Harriet married at sea?) or they were already stationed there when the 69th regiment arrived. Perhaps Samuel was one of the many blacksmiths the army used during the conflict?
I will keep on looking and hopefully find that elusive connection between Samuel, Harriet and John!