Older generation's disputes are really thorns in the flesh.
Especially when you have a relative "A" who is timid + blur and scared of his/her spouse, and ended up causing other relatives to be pissed off.
And now, because of that relative "A", it causes a dispute between other relatives with one "B" unable to let go of the past while another one "C" who is pissed off that "B" cannot let go.
Conclusion:
1) It's just a sorry plight to be the younger generation of these relatives and to be stuck in the situation.
2) Never be one who is afraid of his/her spouse. If not, what's the point of getting married when you are so conscious of your spouse reactions towards your own siblings?
Forget about marrying this spouse then.