I am not a member of this family but had a dear freind (now deceased) who was.
The only other Primeirons I can find are descended from:
Lieutenant-Colonel Prime-Iron Rochfort, a Cromwellian solder, who was shot on 14 May 1652, after trial by court-martial at Cork House, Dublin, for having killed Major Turner.
His most famous descendants were Earls of Belvedere.
The mos recent I can find is Captain John Prime Iron Rochfort, R.N., whose will was written in 1813 and 1818, and proved at London in 1818. He was Irish but his principal heir was one Anna Matilda Rivers alias Rochfort, who was baptised at Lambeth in 1807.
The name appears as Prime Iron, Prime-iron and as Primeiron.
I cannot see how these Primeirons can be related to Primeiron Harris/Grant but as they are the only other Primeirons....
William Good