I didn't even think of that but no way right?!!
No. It was explained way back, but basically his mouse partner went to heat and instincts took over and he hurt his partner. The brother was about to propose too, instead it became a case in which the families settled, and brother & partner broke up (vol 1. ch 5)
oh awwww that's heartbreaking
that's so sad thank you for explaining
did his brother eat his partner?