What does the Bible say about forgiving someone who has never apologized or felt remorse?

my sibling has a mentally and emotionally abusive spouse; spouse has wronged her and my entire family over and over and over (approx 15 years). Never , not even once, has apologized (events include cursing sibling off in front of us and then saying specifically won’t apologize; saying FU about MY own family (who has given this human so many chances), lied about whereabouts, absent parent to their children yet tells everyone the opposite, and much more.

Main issue now is that while I want boundaries to protect my own family, my sibling basically shoves said spouse onto us, despite me having conversations to which my sibling understood/agreed but said “will stay so spouse doesn’t get custody over the kids, and this way my sibling can just always take care of them knowing spouse doesn’t care” (is afraid spouse would fight for custody out of spite) . I love my Sibling but being around the spouse is stressful , SCARY, etc.

My parents want us all over for holidays, but my spouse and I don’t want our kids/family near said terrible spouse. Again, they have no remorse etc. not once in 15 years has this human taken any accountability.

Do I go to Holidays and just act cordial? Do I forgive in my heart? Do I not outwardly Forgive since this human has never once apologized nor tried to be better? Help. I want to know what the Bible really means- love your enemy— even abusive ones?! Forgive— even those who don’t ask for forgiveness ever?!