It’s a yaoi where the older uke takes in the younger seme and raises him. The uke is a gangster but really a good person, and raises like a bunch of Pomeranians. There’s also a story for the gangster uke’s younger brother who is also a loan shark and ends up sleeping with his seme who owes money because his father disappeared after amassing a huge debt. Overall both light hearted series.
this one? Gohoubi wa Shitsuke no Ato http://www.mangago.me/read-manga/gohoubi_ha_shitsuke_no_ato/
The uke is an assassin I think nicknamed black dog or something? And he was afraid of only cats...he ended up being an experimented on super soldier. He was supposed to assassinate the seme but the seme tricked him and captured him using a cat.
http://www.mangago.me/read-manga/darkness_hound/ Is this the one you're talking about?
Both couples were so chaotic and unconventional hahaha loved it