In 2019, as the trailer made clear, all three generations of the family members named John Shaft exist in the Warner Bros-New Line Cinema-Netflix sequel confusingly also entitled "Shaft". Further to add confusion, with three lead characters sharing the same name, from the original MGM version, the family tree relationships are broken down as; Richard Rountree as (uncle/great-uncle) John Shaft, Samuel L Jackson as (nephew/father) John Shaft (Senior/II from RR version), and Usher as (great-nephew/son) John Shaft (Junior/II from SLJ version/III from RR version).
At one point in the film Samuel L. Jackson tells his son that he got a real Super Bowl ring from L.T., referring to former NFL player Lawrence Taylor. This is also likely a reference to the previous Shaft (2000) in which Taylor appeared, although he was not playing himself but an actual character in the film.
The trivia items below may give away important plot points.
In the 2000 film Shaft, Richard Roundtree is introduced to us Samuel L. Jackson's uncle. In the 2019 film, Jackson remarks that Roundtree "was a great father, once you stopped pretending to be my uncle". This is no doubt a way to resolve the conflict between the two narratives.
Shaft II complains about being compared to Laurence Fishburne. This is no doubt inspired by an infamous incident in which Jackson dressed down KTLA (Los Angeles) reporter Sam Rubin, who thought he was interviewing Fishburne.
In this film, it is explained that John Shaft I (Richard Roundtree) was only pretending to be the uncle of John Shaft II (Samuel L. Jackson) in Shaft (2000), and is in fact his father. Late in the film, Jackson asks Roundtree if he remembers when he told him that he was his uncle.