look for some NTR, which either involves another shota kid, stealing the mom away, or another adult stealing the mom away from the son, the son doesn't need to have sex(be a lover of the mom before hand, though it doesn't really matter) with the mom, just her leaving her family at the end.
some examples would be
Sanbun Kyouden- his work. (think I have read all on this site though feel free to post , if he has more on any other site, feel free to share, )
Hana Hook-"" ^same as above
some examples : The Village of Snow Sand, Sinful Mother, Haha to Ikemen x Boku to Zurineta, Hahaoya Shikkaku: Watashi to Musuko no Mesu Buta Netorare Fukushuugeki
some examples would be
Sanbun Kyouden- his work. (think I have read all on this site though feel free to post , if he has more on any other site, feel free to share, )
Hana Hook-"" ^same as above
some examples : The Village of Snow Sand, Sinful Mother, Haha to Ikemen x Boku to Zurineta, Hahaoya Shikkaku: Watashi to Musuko no Mesu Buta Netorare Fukushuugeki