3 year old and abuse


So I don’t really know where to begin, at the weekend Friday to be exact my daughter disclosed to her child minder, “I saw his thingy and he asked me to touch it, but I said no” this is my partners teenage son she accused. Obviously we have had authorities involved she’s repeated it to myself and police/social services. My partner doesn’t want to believe it, it’s his son we had him every weekend and he will now never ever be near her again. I don’t know how we are meant to move on as a family. I obviously believe her I can’t see how a three year old could make something up like that. Anyone got any advice, I’m struggling we all are. I don’t know how to move on or what to do for the best. The boy in question has denied everything. Thanks for reading.