Just found that Constance Otto's husband Charles was still alive on the 1871 so Montague Leverson not necessarily a suspect as the father of any of her children. Odd that he was neither a boarder nor lodger in 1880, just undefined.
No sign of him in 1870 nor (unsurprisingly) in the 1890 fragment. He was however on the 1900 I think as Montague K Leverson in Brooklyn, New York described as Physician which is odd, but born England 1830 which is right - original could be R. In 1910 I found him twice! Lodger in the Bronx, New York, boarder in Atlanta Georgia. Details correct both times, down to "Own Income" under Occupation. Perhaps the census was carried out over a few days and he was counted twice, perhaps counted both where he actually was and at his usual abode - I've a couple of examples of this in my own tree. In all three entries he is Widower.
Only England census I see him on is the 1851 still at home, not long after that unfortunate incident with the shotgun.
Chris