Richard Eva, born about 1836, son of William and Maria (nee Dodd) appear on my tree. Richard is a first cousin, 4 times removed. The last information I have on Richard is from the 1851 census. By 1861 he wasn't living at home with his parents, but doesn't appear to be anywhere else in the 1861 census either. You saying about him being in the Royal Engineers in Gibraltar and later in Malta could explain this.
Do you have any other known details which could then be checked out.