Here's a more complete answer:
Mattes Dornblum IS the same person as Joseph Dornblum. Joseph/Mattes and his son Max/Meyer and family are all buried in the Mount Hebron Cemetery in Queens. There's a photo of Meyer's matzeiva online, and it gives his name as
נתן מאיר בר יוסף מתתיה הכהן
https://www.findagrave.com/memorial/77475262/meyer-dornblumhttps://images.findagrave.com/photos/2017/49/77475262_1487546472.jpgIn Europe, he was known as Mattes (based on the name his friend and nephew gave for the ships manifest when they immigrated) or Jossel (based on name he himself gave at immigration). In the 1910 census, he gave his name as Max and his son as Nathan! In the 1920 census, he is Matthias and his son is Max. In the 1930 census and thereafter, he is Joseph and his son is Meyer.
Joseph/Mattes and his wife Lena/Lea had two children who lived with them in America.
Meyer/Nathan/Max (1896-1978) and Bluma (1902-1982).
Joseph/Mattes arrived first, in 1909, his son Meyer arrived in 1910 (under the name Nussem Dernblum on the ships manifest - probably Nussen) and Lea/Lena arrived with Bluma in 1912. This kind of "chain migration" was common among poor Russian Jews - The father would go first, save money for a ticket for the next person, and so on. So they were probably not well-to-do. Joseph/Mattes said he was a tailor, and he may well have worked in that profession in Russia. However, Russian Jews knew that workers were needed in clothing manufacture, so many called themselves tailor when they immigrated.
Meyer/Max married Fannie Katz and had a daughter Ann (1917-2007). Fannie died the following year, in October 1918. I haven't looked for her death certificate, but October 1918 is famous for having had the peak deaths of the 1918 flu pandemic, when 195,000 Americans died from that cause. Maybe she was one of the victims.
Meyer/Max moved back with Annie, to live with his parents and Bluma, and was there in the 1920 census when Annie was 2 years old. However, he remarried, to Sadie Espass, soon after that census, and had two more daughters: Sylvia (1921-2013) and Pearl (1930-2000). Pearl shortened the name to Dorn, and Sylvia's name was always Dornblum, so it seems that neither of them ever married, and had no children. Sylvia's obit says:
DORNBLUM--Sylvia. May 8, 1921 - May 2nd, 2013. Loved by her friends. Services Sunday at 12 noon from Schwartz Bros. Jeffer Memorial Chapel, 114-03 Queens Blvd., Forest Hills, NY. Interment at Mt. Hebron Cemetery alongside her beloved sister Pearl.
Anne Dornblum also seems to have never married and had no children, so there are no descendants from Meyer/Max.
But Joseph/Mattes' daughter Bluma does have living descendants.
In 1925 and 1930, Joseph and Lena, with their daughter Bluma, lived in East Nassau, in Rennselaer County NY. This is a rural area, and perhaps they moved there to try their hand at farming, which was a thing to do back then. In 1925 Joseph said he was a tailor, but in the 1930 census, he said "farmer". Lena died in 1932, and is buried in Queens. I haven't found where Joseph lived after this date, but he was buried in Queens in 1948.
In 1931, Bluma married Joseph Nudleman (1892-1966), and by the 1940 census, they were living in Port Jervis NY with their two children, Eleanor and Seymour, AND their niece, Ann/Annie/Anna Dornblum.
It's in Ann Dornblum's obituary (2007) that you can find the names of Bluma and Joseph's descendants, Eleanor and Seymour, who were Ann's cousins, as well as their children and grandchildren. That would be the place to start looking for living descendants!
https://grayparkerfuneralhome.com/tribute/details/16/Ann-Dornblum/obituary.html