Emperor Keikō

was the 12th emperor of Japan, according to the traditional order of succession. Historians consider Emperor Keikō to be a legendary person; and the name Keikō"-tennō" was created for him posthumously by later generations.
No certain dates can be assigned to this emperor's life or reign. The conventionally accepted names and sequence of the early emperors were not to be confirmed as "traditional" until the reign of Emperor Kammu, who was the 50th monarch of the Yamato dynasty. 
Traditional history.
Keikō is almost certainly a legend; but the "Kojiki" and "Nihonshoki" record his name.
Events of Keikō's life.
The limited information about Keikō does not imply that no such person ever existed. Very little information is available for study prior to the reign of the 29th monarch, Emperor Kimmei. 
In "Kojiki", Keikō sent his one of his sons to Kyūshū to fight battles on his behalf. In "Nihonshoki", Keikō fought and won these battles against local tribes. According to both sources, he sent Yamatotakeru to Izumo province and eastern provinces to expand his territory.
After his death.
This emperor's official name after his death (his posthumous name) was regularized many centuries after the lifetime which was ascribed to Keikō.
The actual site of his grave is not known. According to the Imperial Household Agency, this emperor is venerated at a memorial Shinto shrine ("misasagi") at Nara. The "kami" of Emperor Keikō is also venerated at Anaho jinja in Anaho, Ōmi province.
Spouses and children.
Empress (first): Harima no Inabi no Ooiratsume (播磨稲日大郎姫), daughter of Wakatakehiko (若建吉備津日子)
Empress (second): Yasakairihime (八坂入媛命), daughter of Yasakairihiko (八坂入彦命)
Mizuhanoiratume (水歯郎媛), daughter of iwatsukuwake (磐衝別命), younger sister of Iwakiwake (石城別王)
Ikawahime (五十河媛)
Abe no Takadahime (阿倍高田媛), daughter of Abe no Kogoto (阿倍木事)
Himuka no Kaminagaootane (日向髪長大田根)
Sonotakehime (襲武媛)
Himuka no Mihakashihime (日向御刀媛)
Inabinowakairatsume (伊那毘若郎女), daughter of Wakatakehiko, younger sister of Harima no Inabi no Ooiratsume
Igotohime (五十琴姫命),　daughter of Mononobe no Igui (物部胆咋宿禰)