My condolences DR on the loss of your sister.
Losing a sibling is idk, its actually indescribable. Having multiple siblings doesn't make up for the gaping hole, and time?.... well time just helps us to adjust to said gaping hole. You never get to refill that space, it just gets easier to accept, as the pain lessens with the years that go by.
I've read and re-read your OP and still cannot wrap my head around your FOO. The only words I have to describe them are not permitted by PC guidelines...
I'm glad you are protecting your daughters and their emotional wellbeing from these "people".
May your sister rest in peace and may you find solace in your time of grief.