Kemutai Ane to Zurui Imouto

Jun and Toran, two sisters who had been estranged from each other, are reunited after the death of their mother. The reason why they were separated in the first place was because of one man, Ritsu. Ritsu used to be Jun's boyfriend, but now he is Ran's husband. The three of them end up living under the same roof...

(Source: Kiss Comic, translated)