Responses
What is the title?
Resonance: Heat (part1)
Resonance: Lust (part2)
You can find the link on novelupdates. Read on the translators website.
The youngest brother's name is Kouki^^, he is a 23 year old alpha, he is younger than the omega Amane. They work for the police, Kouki is a rookie here.
Thanks
If anyone is interested, someone started to translate the novel about Keiki's younger brother who works for the police. That novel came before this novel/manga. You can find the link on novelupdates.