The twins Hugo and Otto were born on the 1st of February 1858 at Lobzów near Krakau (Kraków) as sons of Oberleutnant Eduard Meixner. Besides their similar looks as was common with twins there were amazing parallels within their lives especially during the first decades. After successfully graduating from the military college at St. Pölten and the military academy at Wiener Neustadt they were both promoted to Leutnant in infantry regiment number 55 on the 1st of November 1878. Both attended the same class at the Kriegsschule and were attached, in the meantime promoted to Oberleutnant on the 1st of May 1883, to the general staff corps.
Otto Meixner was attached to the headquarters of the 22nd infantry brigade and then that of the 34th infantry division. Later he was assigned to the operations department of the general staff corps at Vienna where he received his promotion to Hauptmann 1st class on the 1st of May 1886. On the 19th of November 1889 he married Margarete, a daughter of Generalmajor Johann Ritter von Kubin and his twin brother Hugo married on the same day her sister Auguste! From the 1st of May 1890 to the 1st of October 1891 he was performed line duty with infantry regiment number 54 at Olmütz. After this routine duty with the troops Otto Meixner was appointed as an instructor for "Train-, Kommunikation- und Verpflegswesen" at the Miliär-Intendanz-Kurs and the Verpflegsverwalter-Kurs (Train, communications and supply matters at the military intendance and supply administrator's courses). At this teaching assignment he received his promotion to Major on the 1st of November 1892. On the 25th of December 1894 he was transferred to the Technischen und Administrativen Militär-Komitee and again engaged as an instructor but now on the higher administrativel military course. After his promotion to Oberstleutnant on the 1st of May 1895 he was appointed chief of the 3rd section of the technical military committee on the 23rd of October 1896. For his successful performance there he was honored with the award of the Military Merit Cross on the 2nd of September 1897. Simultaneously he was transferred for line duty with infantry regiment number 35 in Pilsen where he received his promotion to Oberst on the 1st of May 1898 with seniority from the 21st of May. On the 1st of April 1899 Otto Meixner assumed command of infantry regiment number 13 in his hometown of Krakau (Kraków).
As was normal he received after four years of commanding a regiment the 3rd class of the Order of the Iron Crown on the 18th of April 1903. On the 9th of August 1904 he took over command of the 41st (Landwehr) infantry brigade at Pilsen shortly followed by his promotion to Generalmajor on the 1st of November 1904 with seniority from the 4th of November - still one day "better" than his twin brother Hugo. On the 1st of December 1907 he received his appointment as Sektionschef of the k.k. Landesverteidigungsministerium (Section chief in the Austrian ministry of defense). While his brother Hugo held an important post in the administration of the k.u.k. army, Otto Meixner now held an important post in the administration of the k.k. Landwehr. The Landwehr ministry had only seven sections, three from the political and four from the military part. The four heads of section of the military part were the most senior military official of the Intendance, the senior judge-advocate and two generals which de facto were the right and left arm of the minister of defense. In the case of Otto Meixner this was the later Generaloberst Friedrich von Georgi. Uniquely in the practice of ennoblement, the twins Otto (9th July 1908) and Hugo (5th August 1908) were granted to right to carry the same predicate "von Zweienstamm". On the 1st of November 1908 Otto Meixner von Zweienstamm was promoted to Feldmarschall-Leutnant with seniority from the 3rd of November. His outstanding performance at the defense ministry was honored with the award of the knight's cross of the Order of Leopold on the 25th of February 1910. On the 23rd of October 1911 he received the commendation of the Kaiser which allowed him to wear the Bronze Military Merit Medal (Signum Laudis) on the red ribbon. On the same date he received the appointment to command the 4th infantry division at Brünn. On the 25th of July 1912 Otto Meixner von Zweienstamm received the temporary appointment as commander of the 7th corps at Temesvár, this appointment becoming a definitive one on the 1st of October of the same year. On the 2nd of April 1913 he was honored with the title of Geheimer Rat (Privy Chancellor) shortly followed by his promotion to General der Infanterie on the 1st of May 1913 - seven month and one day earlier than his twin brother Hugo!
At the start of the war his corps was part of the B echelon initially assigned for the invasion of Serbia, but with the changing priorities following Russian mobilization and involvement in the war, the planned participation of 7th corps in the invasion of Serbia was never executed and the 7th corps was left to secure the junction of the Save and Danube rivers for the first two weeks of August 1914. The disintegration of the third army's front in Galicia necessitated the transfer of the remainder of 2nd army to eastern Galicia. However by the time of their concentration a fortnight later, the whole front was in retreat and the Russians swept westwards towards the Carpathian mountains. These initial reverses led to a major shakeup amongst the less successful army and corps commanders who where replaced using the euphemistic term - "health reasons". Otto Meixner von Zweienstamm was retired to Vienna on the 7th of October 1914 and never again returned to active duty. After the war Otto, in contrast to his brother Hugo, was often seen at veterans' meetings and became president of the Vereinigung Alt-Neustadt, the society of former graduates of this military academy in 1926. He held this post until 1937 when he accepted the role of honorary president of this society. General der Infanterie Otto Meixner von Zweienstamm died on the 10th of October 1946 at Mondsee in Upper Austria but his body was transported to Vienna where he was buried like his brother would be in the family grave at the Hütteldorfer Friedhof in Vienna's 14th district.