Fred and Betty Hamburger, and their two daughters Irene and Carol, are the only familial relatives that we have had. Luckily, for a number of years they were close enough to develop a relationship. This relationship echoed earlier, closer, relationships that Dad's parents had with Fred's parents.

Letter Dad wrote after Betty Hamburger died.

The news of Betty's death distressed us greatly even though it was to be expected and under the circumstances brought relief to all concerned. Yet the finality of it all is difficult to accept.  Betty and all of you have gone through torments in the past months because, even with the best intentions, noone could relieve her suffering.  Many times we asked ourselves what, if anything, we could do to help knowing fully well that there was no recourse.  We don't have to tell you how fond we were of Betty, how we appreciated her efforts to strengthen the family and promote its values.  In view of the loss of so many family members and ties as the result of Nazi terror I (Henry) especially appreciated her efforts and felt closer than family blood ties actually called for.  Perhaps this is a good time to reminisce and remind you of our relationship.  In 1866 my grandmother, Helene Hamburger, was born in Poznan (Kempler), later Germany.  She had one brother Siegfried, father of Alice Hamburger whom Fred knew in New York.  The two lost their parents early in their teens[1] and were taken in by their paternal uncle and aunt[2] to be raised with their children.  Luckily they all got to love each other very much that eventually they considered each other siblings rather than cousins.[3]  One of them was Fred's grandfather who married a Margaret Lachman and lived in Breslau[4].  Unfortunately he died early in life, I never knew him.  But I was a great fan of "Tante Grete" who became somewhat of a matriarch of the Hamburger family.  We spent many happy hours at her place, and celebrated festivals together.  Of course Fred's family lived in Berlin.  But two of his uncles were in Breslau, Ernst (the father of Eva, Erica and Walter) and Hans who married later on and had no offspring (?).  My grandmother died in 1929 or 30 - but she also had close contact with the other Hamburgers who were a closeknit tribe.

Notes:

1. Helene and Siegfried were children of Hirsch Hamburger (who dies in Kempen in 1876) and Auguste (Jereslaw) Hamburger (who dies in Kempen in 1871). Thus, Helene would been 10 when her father died (even earlier than early teens, but good enough). 

2. These are the mystery people. Going by Dad I attributed the unnamed paternal uncle as being a brother of Hirsch Hamburger and the father of Julius Hamburger (see below).
   
   However, I ran into trouble now when I found this Hamburger tree on Ancestry.com. While it includes Hirsch and Auguste and Helene with the right dates, it also shows two older sisters for Helene and no brother. More importantly, it shows Hirsch's father Zacharias Hamburger and his wife Lewie Baruch with 11 children, 7 of which were male, none of them name Julius. Of these, two (Baruch and Abraham) died before Hirsch. Of the other four, none of them show any sons with the names of Ludwig, Ernst, or Hans (although, as an aside, two of them--Meyer and Solomon--have sons named Siegfried).
   
   So, now going to MyHeritage.com and Geni.com, I find several trees with another son of Hirsch, born in 1852, named Jonas Julius. I also see some other children, but still no Siegfried. So, my new theory is that Helene was not raised by her uncle, but by her 14-year-older brother Jonas Julius. He would have been 24 when their father died. However, one tree says he wasn't married until 1882, which means Helene would have been 16. 

3. So, who did Helene and Siegried consider a sibling, rather than a cousin?! If one believes [2], then they were actually with a sibling. Once he had children, they would have been nieces and nephews.

4. I have found that a Margaret Lachman was married to a Julius Hamburger, born in 1852. This is confirmed by a 1891 JRI-Poland birth record for Fred's father Ludwig Hamburger, showing his father as Julius Hamburger and his mother as Grete Lachmann.