I will help! Ok, so all of them start with "Kuroneko kareshi" except for 6 and 6.1 (side story) so I'm just going to give the last word cuz I'm lazy.
1. No Asobikata
2.No Amaekata
3. No Nakasekata
4. No Aishikata
5. No Afurekata
6. Kuroneko to kareshi to ouji
6.1 Fukigen Kareshi no saraikata
7. No arukikata
Sorry if you already found this list.
Spinoff mentioned in this volume http://www.mangago.me/read-manga/nekoka_danshi_no_shitsukekata/
5 Fukigen Series (Side Story of 4) - Big Bro x Caretaker
-- 5.1 Fukigen kareshi no Nadamekata
-- 5.2 Fukigen kareshi no Saraikata
Totally copied from another comment lol cuz...lazy.
Then this is the last that I know of. Nephew all grown up. http://www.mangago.me/read-manga/wagamama_ouji_wa_neko_wo_karu/
1. Kuroneko Kareshi no Asobikata
2. Kuroneko Kareshi no Amaekata
3. Kuroneko Kareshi no Aishikata
4. Fukigen Kareshi no Nadamekata
5. Nekoka Kareshi no Ayashikata
https://www.comicforum.de/showthread.php?146447-Kuroneko-Reihe-Aya-Sakyo
You should also check this out... There are also a few informations
1 Kuroneko Kareshi no Asobikata - Shingo & Keiichi's Love begins.
2 Kuroneko Kareshi no Amaekata - A Lover's Quarrel
3 Kuroneko Kareshi no Nakasekata - Move to live together as a couple
4 Kuroneko Kareshi no Aishikata - Interfered by Arrogant Bro/ WereLeopard Clan Leader
➽ 4.1 Fukigen kareshi no Nadamekata (Side Story) - Big Bro x Caretaker Eli
5 Kuroneko Kareshi no Afurekata - Shingo's opponent appears.
6 Kuroneko to Kareshi to Ouji - "Shingo, pls look after me~" said puppy-eyes Rio.
➽ 6.1 Fukigen kareshi no Saraikata (Side Story) - Eli & Jin travel to save his cousin Sara.
7 Kuroneko Kareshi no Arukikata - Shingo re-encounters a Calico Cat, Kokonoe.
in which order do i have to read the manga (where do i start) since this is not the beginning of the story