Boris Nikolaevich Delaunay or Delone (Russian: Бори́с Никола́евич Делоне́ ; March 15, 1890 – July 17, 1980) was one of the first Russian mountain climbers and a Soviet/Russian mathematician, and the father of physicist Nikolai Borisovich Delone.
Nikolai Delaunay, Jr. (aka Delone, Nikolai Borisovich) (22 May 1926 – 11 September 2008) was a born in Leningrad, USSR (now Saint Petersburg, Russia).
In mathematics and computational geometry, a Delaunay triangulation for a given set P of discrete points in a plane is a triangulation DT(P) such that no point in P is inside the circumcircle of any triangle in DT(P).
 Delaunay triangulations maximize the minimum angle of all the angles of the triangles in the triangulation; they tend to avoid sliver triangles.
 The triangulation is named after Boris Delaunay for his work on this topic from 1934.
Prince Nikolai Borisovich Yusupov (Russian: Князь Никола́й Бори́сович Юсу́пов ; 26 October [O.S. 15 October] 1750 – 15 July 1831) was a Russian nobleman and art collector of the House of Yusupov.
Nikolai Borisovich Kolesov (Russian: Николай Борисович Колесов ; born February 16, 1956; died August 23, 1998) was a Russian professional footballer.
 He made his professional debut in the Soviet Top League in 1976 for FC Dynamo Moscow.
The Trachtenberg system is a system of rapid mental calculation.
 The system consists of a number of readily memorized operations that allow one to perform arithmetic computations very quickly.
 It was developed by the Russian Jewish engineer Jakow Trachtenberg in order to keep his mind occupied while being held in a Nazi concentration camp.
Prince Nikolai Borisovich Golitsyn (Russian: Николай Борисович Голицын , alternatively spelled Galitzin; 8 December/19 December 1794 – 22 October/3 November 1866) was a Russian aristocrat, of the Galitzine family.
 He was an amateur musician, and is known particularly for his commissioning three string quartets — opp.
 127, 130 and 132 — from Ludwig van Beethoven, which are among the composer's group of late string quartets.
 His parents were Boris Andreevich Golitsyn and his wife Ana, whilst one of his sisters was the philanthropist Tatiana Potemkina.
Jakow Trachtenberg (17 June 1888 – 1953) was a Jewish mathematician who developed the mental calculation techniques called the Trachtenberg system.
Nikolai Borisovich Kopnin (May 17, 1946 – October 20, 2013) was a Russian physicist specializing in superconductivity.
Nikolai Borisovich Obukhov (Russian: Николай Борисович Обухов ; Nicolai, Nicolas, Nikolay; Obukhow, Obouhow, Obouhov, Obouhoff) (22 April 189213 June 1954) was a modernist and mystic Russian composer, active mainly in France.
 An avant-garde figure who took as his point of departure the late music of Scriabin, he fled Russia along with his family after the Bolshevik Revolution, settling in Paris.
 His music is notable for its religious mysticism, its unusual notation, its use of an idiosyncratic 12-tone chromatic language, and its pioneering use of electronic musical instruments in the era of their earliest development.

Question: Which mathematician was the father of physicist Nikolai Borisovich Delone: Jakow Trachtenberg or Boris Delaunay?
Answer: Boris Nikolaevich Delaunay