This is a rather difficult decision and has been doing my head in for a couple of weeks now.
I will give you some background first. I am male 24, I am in a (sort of) relationship with a 36yo woman for nearly 3 years now. She has two daughters who are 20yo and 18yo, they both have boyfriends.
They are a very open family in many ways, they talk to each other about anything, they all opening admit to being bi-sexual and talk about it....a lot, they all sunbathe topless by their pool even when guests are around. I found that difficult and embarrassing to deal with at first but it is just second nature now and I don't bat an eyelid.
Now the issue that I would like advice/opinions on is rather disturbing in many ways so I will just tell it as it happened and let everyone make their own judgements.
I have a key to the house, I went around a couple of weeks ago and let myself in. As far as I knew no-one was home. I went to the kitchen to get a drink and saw the girls out back by the pool. I didn't say hi because I was going to have a shower before I went for a swim.
After the shower I was back in the kitchen and I saw something that I don't even really know how to describe, it made me feel quite ill and to be honest also quite aroused at the same time. The two girls, sisters, were going for it and holding no prisoners. It wasn't just a kiss it was a lot more than that but no need for details. Honestly, I watched for about 15 minutes which I am not proud of but it was just one of those things that even though you know you shouldn't you just can't turn away.
I went back out the front, and opened the garage door to make it look as though I was just arriving and by the time I was around the back at the pool they had their bikini bottoms back on as though nothing had happened. I said nothing. They were both pretty drunk so I thought maybe it's a once off (fingers crossed).
I decided I would not say anything to anyone about this but over the last couple of weeks I have noticed things that I probably didn't pick up on before. The way they touch each other and flirt constantly. The way they kiss goodnight, I never noticed before but now it just seems a little too inappropriate, a little too much lip for a little too long. Last night was like the final straw, hot water was running low as the mum and I just had a shower so they showered together! They are 18 & 20yo! The mum didn't flinch when they said they were showering together, I nearly fell over.
So what do I do?
Do I get involved at all? Do I talk to them? I am only 4 years older than them, not really a 'father figure'.
Do I tell the mum (my girlfriend)? Does she know already? Is it any of my business?
Do I tell the boyfriends?
How do I approach getting involved or do I just leave it and try to ignore it?
I thought to myself if it were a brother/sister I would definitely step in because there could be consequences (pregnancy) but that doesn't apply to two sisters.
It's obviously inappropriate, but at the end of the day are they really hurting anyone?
I doubt anyone would have had a similar experience to offer advice on what they did so I am really just looking for opinions on which way others would deal with it. I am really struggling to choose a direction myself.
At the moment, if it weren't for my feeling towards my girlfriend (their mum) I would just run as fast as I could in the other direction.