Hope I've got the right person!
I'm a family researcher myself and I happened across your queries over the last few years, reference a person called Morenzy. My understanding is that he was a descendant of the Irish De Montmorency family (County Kilkenny). This was a big widespread well-off aristrocratic family in the late 1700's and early to mid 1800's. They were a junior branch of even older and more aristocratic sister families in Europe and UK. The mainland European branch goes back many centuries, and even in Victorian time their links with the Irish branch were already very weak. Some parts of the early family in Ireland and UK were originally called Morres, and their main estates were at Mount Morres. This was convenient because it enabled them to use the name De Mount Morres to strengthen their dying hold on their De Montmorency name....this slight of hand wasn't universally popular with the family fathers in Europe!
Anyway, back to your search. We understand that a wayward great great aunt of mine (Mary Buggy 1775-1850's)was estate secretary at the family estates near Kilkenny in Ireland. She had an illicit dalliance with the eldest son of the family. He was Sir William(II)Evans Ryves Morres (de Montmorency)(1769-1829). The father (master of the estate)was Sir William(I)Evans Morres. The son's dalliance with Mary(1798-1802)produced 2 (under the bedsheets) offspring: William(III)de Momtmorency and Haydock Morres. Son No 2 Haydock got married twice (both to Catherines, I think) and had offspring in the 1820's. Son no.1, William(III) appeared to have led a slightly roughish and wild early life and managed to spend heavily from his father's dwindling estate. After an unconventional start involving his future wife's abduction he actually managed a marriage (1818)to Harriet Ursula Mossum. There were 3 children William(IV), Harriet Ursula, and Louisa. William(III)himself died in mysterious circumstances in Middlesex, England in 1850. We believe he was fond of the bottle, and probably other things too!! Earlier on when the estate was on its knees, after his father's death he had to rent it all out through agents. One of William's agents was unable to evict Mary Buggy (and her relatives) from the house which had been allowed to live in on the estate. In the 1840's there was a major and scandalous court case over this where all the dirt came out, and Mary won! Eventually Mary went, and the Estate was all sold off to pay William(III)'s debts.
I understand that your man was either William(IV)(from Harriet and William(III)s marriage) or one of the other children from Haydock's marriage. William IV would have been born around 1820. It was known he joined the British army, probably 76th regiment, but fate unknown after that. It was also known that all of William(II)'s children, and grand children, were traumatised and shaken, and perhaps shamed, by their families turn of events and there had been talk of emigration and name changing. It was also known that one family member did actually leave, believed with his wife, for USA under an assumed name Demont Morenzy. There were strong connections with the NE of England and Durham, because the family had cousins there, and also because there were family army connections there.
Hope that helps!
Let me know if can be of any further assistance.