As Muslims we must always be forebearing and forgiving, even to those who wrong us. The holy Quran clearly tells us that we must not hold grudges against those who believe. This is in verse 10 of Surah al-Hashr:
And do not put in our hearts any rancour towards those who believe.
Regarding someone being family and kin, we know how Islam emphasises on observing the best of conduct regarding one's family. There will always be disputes and disagreements, but a believer must never harbour any resentment towards another believer.
What we can say is we leave what they did for Allah ta'ala to deal with.
With prayers for your success.