Oh dear! I hope I did not give the impression that I think social workers or other professionals are vindictive or looking to sanction people...I'm terribly sorry for creating that idea!
No, you didn't give that impression at all.
just, as piratelvr said - you seemed to be hesitating, and i know that people sometimes hesitate because they are afraid of causing more harm than good, or of 'making waves" unnecessarily, or becuse they are afraid that CPS are overworked and don't want to "bother " them over something that may or may not be valid. let the professionals decide if Sis is telling the truth or not.
I hope things work out for these children.