100% certain. Read about it E.R. Bevan's
The House of Seleucus: Volume 2 countless times, and I think B. Bar Kochva mentioned it in his notes in his book
The Seleucid Army. Here's a link to a site that I use every so often for quick summaries of the lives and accomplishments of Seleucid, Antigonid, and Lagid kings:
http://www.livius.org/am-ao/antiochu...ochus_iii.html
It certainly was the custom for the early Seleukid kings to name their sons after their fathers, but Seleukos II started the 'trend' where the eldest son was named after one's self. Seleukos II Kallinikos was initially succeeded by his eldest son Seleukos III Keraunos who had one of the shortest, if not the shortest, reign of any Seleukid king (though the later ones come pretty close) and Seleukos was then succeeded by his younger brother Antiochus III.
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