I'm excited that a new possible cousin, you, has appeared!
I've been mostly looking at the 1940 censuses lately & I did find John Sampson & Bertha Lewis.http://mediasvc.ancestry.com/image/9b9867754cc682205ede49570...
The question of Harry's relationship is, at least, sorted out with this census. Bertha Lewis is the person noted as giving the information for the census.
On the 1930 census, Harry followed John Francis who'd been listed as "son" to the head of the household John Sampson Lewis. Harry's relationship to the head of household had been listed as "nephew" which was crossed out & "son" entered leading to much confusion given his placement on the census & family biology which I touched on in my Sep 08 series of replies.
On this 1940 census, Harry once again follows John Francis who is still noted as "son" but this time around Harry's status is "grandson" to the head of the household. His placement after John Francis implies that he was John Francis' son.
Other of John & Bertha's grandchildren are also in the household & are placed just after their parent so this placement of John Francis followed by Harry is consistant with that pattern.
With the finding of this 1940 census entry, I'm fairly certain that Harry was John Francis Lewis' son & a grandson to John Sampson Lewis & wife Bertha nee Skerritt.
And given that you say Harry's middle name was "Samson" - there's probably a "p" in there but I don't know if the omission here is just a goof or if your family has the name w/o the "p" - that's pretty strong evidence taken with everything else for calling Harry the son of John Francis Lewis & hyis elusive wife Kate.
At any rate the middle name "Sampson", I've recently discovered, comes from John Sampson Lewis' mother. Her maiden name was Sampson.
Obtaining a birth certificate for Harry would really cement the deal! A death certificate & obit would round things out nicely.
I can't get these certificates because of the privacy laws.
However, as a direct descendant/relation you can. Have you or your mother sent for any of these?
An obit if there was one, would be in the Staten Island Advance.
If I could get only one certificate, birth would be my first choice because the information would be being supplied by the principals involved - mother or father usually & at this point in time, still a home birth but maybe attended by a midwife or doctor who also might have been the one giving the information. And the BC might shed some light on the ever elusive mom, Kate.
A quick check of the NYC Vitals site reveals that for a birth certificate, you'd have to request it by mail. If you could get your mother to request her father's birth certificate that might be even better because she's the daughter & not one generation removed as you are.
A death certificate can be ordered via internet but it appears that NYC uses the company VitalCheck for order processing so that adds another $8.50 servicing charge to the $15 cost of a certificate.
I don't have a complete DOD for John Francis Lewis whom I'm almost certain now was Harry's father. Just a year - 1961. The date on the grave marker is unreadable in the photo @ Find A Grave.
Are you or your mother near Staten Island? You could go out to Fairview Cemetery, Castleton Corners & actually look at the marker to see what date is on it. The marker was in sad shape in 2008 when the photo on Find A Grave was taken & I hope it's still there. The grave location is Plot Q 197.
Here's the Find A Grave link to John Francis Lewis' memorial: http://www.findagrave.com/cgi-bin/fg.cgi?page=gr&GSln=le...
The other person in the grave, Ethel Skerritt, was John's spinster aunt - his mother Bertha's youngest sister.
Assuming Harry was John Francis Lewis & Kate nee unknown's son, then he was possibly known by the nickname "Dougie" and had siblings John b. Sep 1917 and Katherine aka Honey b.Feb 1919.
Click on my name to contact me via the Ancestry contact system & we'll be able to exchange addys so as to collaborate more on Harry.