Your own farts smell good to you.
The farts of another person do not.
The odour from farts are caused by the bacteria in your body digesting the food you consume.
Theory: Your body enjoys the smell of its own bacteria but not the smell of the bacteria in other people’s bodies.
It is possible that the bacteria of your immediate family members have some bearing on whether you find them palatable.
It is highly likely that the bacteria in your Mother’s body is more pleasant to you, especially at an early age, than any other family member.
Two people in a close intimate relationship may eventually exchange enough bacteria, or become used to the bacteria, that they no longer find each other’s farts offensive.