Turned in to a 3sum

I've been in a relationship with my 21 year old nephew for the last 3 years,we done a homemade movie and i showed my sister when she came round, surprised she watched it all,I was surprised that she wasn't mad at me in fact she wanted to no details,I told her everything and she said you lucky b**** what i would do to get f***** by someone with a big c***,told her he's coming round and it could be arranged,we ended up having a 3sum,I watched for 10 minutes as he f***** the s*** out of his own mom,she was soaked with sweat and panting, at least once a week we get together.