Seven years into our marriage, my 27 y o SD asked to move in, with her 6 and 3 y o boys. She had just been evicted (first I had known about it). She has a history of disrespect toward me, swearing, yelling, name calling...

My husband does not ever stand to her...if he tries she will threaten to withhold the grandchildren’s company from him. 

I told my husband I felt it wouldn’t be good for us or our marriage for them to move in. Arguing ensued, he finally told her she could not (but didn’t represent us as a unified front, said I was the one saying no).