User blog comment:B214/DxD Zero: Sirzechs story/@comment-2601:8C:601:5692:D919:FA4C:E275:E121-20180804150855

So the Japanese wikipedia article finally updated with the new Maou children's names (unfortunately nothing on King of Flies, though). Here they are, along with my suggested TLs:

Beedleid Basharn Beelzebub ビドレイド・バシャルン・ベルゼブブ Tsufarmé Teleac Leviathan ツファーメ・テレアク・レヴィアタン Damaidos Zereikel Asmodeus ダマイドス・ゼレイケル・アスモデウス

Note that each first name seems to be three syllables, the Beedleid should be pronounced "Bee-Dol-Aid/Id".

Also, thanks to DxDFan's link, we have confirmation that 紅髪の滅殺王子（ルイン・プリンス） is read as "Benigami no Ruin Prince" and thus TLs as "Crimson-haired Ruin Prince", paralleling Rias's "Crimson-haired Ruin Princess", as I thought.