<human>: Hi guys!

Cutting right to the chase, my Uncle Mark was once accused of raping his brother Edward when they were 14 and 10 respectively. The whole family pretty much came to the conclusion that Eddy was lying and that was that. This all happened around 20+ years ago.

Skip to present day, Mark has divorced his wife and his two daughters (15 and 13) no longer keep any contact with him, this is all extremely taboo and no one will talk about why. This is the first thing that worries me.

My mother (batshit crazy) believes that he is a saint and will often let my sister sleep over his house maybe once a month or so because "she has fun there", some context, he lives on a farm has motorbikes and other fun stuff, also happens to be extremely wealthy.

My sister seems to be indifferent about going there, and I'm just asking, is there a way I can ask an extremely innocent 12 year old if anything is happening that shouldn't be happening, she has previously lived with him (my mother was having some financial hardships and is also divorced) so I fear that he may have enough emotional control over her for her to never tell me if it was happening.

Thanks in advance for any and all replies.

Condense the text into a few key points
<bot>: Fearing that my sister is being sexually abused by my uncle who has has rape allegations in the past and has two daughters who no longer keep contact  with him for unknown reasons.