Luciano wasn't Maranzano's underboss, he was a captain under Masseria. The all already existed by the 1920s. The idea that they were formed after the war is a myth that stems from Valachi's misunderstanding of what was going on around him.

At the start of the war, the bosses were:

Nicola Schiro
Joseph Profaci (recently taken over from Salvatore DiBella)
Alfred Mineo (replaced the murdered Salvatore D'Aquila)
Joseph Masseria (also capo dei capi)
Gaetano Reina

Following Masseria's murder, the bosses were:

Salvatore Maranzano (also capo dei capi, took over from Schiro after he fled)
Joseph Profaci
Frank Scalise (replaced Mineo following his murder)
Charles Luciano (replaced Masseria)
Thomas Gagliano (replaced the murdered Joseph Pinzolo, who briefly took over from Reina)

Then following Maranzano's murder, Bonanno replaced him as boss of that family and Mangano replaced Scalise as boss.