Sibling child care?

https://www.mangago.zone/read-manga/brother_am_i_cute_lovena_luv/

https://www.mangago.zone/read-manga/brother_am_i_cute_lovena_luv/

https://www.mangago.zone/read-manga/duke_s_private_tutor/ but the childcare is not the main plot point


https://www.mangago.zone/read-manga/sweet_home_mofumofu_tanuki_kyoudai_to_kazoku_ni_narimasu/ once again. Not the main plot point but they meet because of his younger brother