Diary Blunder

A few weeks ago I helped my grandad sort through some of my nans stuff. It had been a year since she passed away, so I offered to help.
When he was downstairs I opened up a box and saw a small black diary in it.
I called to my grandad, but he didn't hear me. Intrigued I opened up the diary and immediately realised it was a sex diary.

That's because pasted inside was a picture of my grandad fucking a younger girl. The comment said "Me, taking a picture of **** fucking *****".
There were other pictures in there too. Ones showing my nan having sex with another man, but mostly of my grandad fucking various younger women.

But the picture that really had my attention, was the one showing my grandad lay on the bed naked, holding his huge erect penis.
Each diary entry, was about a night of sex between my nan and grandad, or about either of them having sex with other people. But the vast majority were my nans comments about my grandad fucking girls around my age.

And it definitely appeared as though my nan was into watching him fuck these girls.
When my grandad eventually came back upstairs, I quickly put the diary back in the box.
However when he took it out, he smiled at me as though he knew I'd seen it. He didn't say anything, but I'm sure he had a tent in his jogging bottoms.
It's been a few weeks now since helping him sort my nans things, and I've been round a few times.

Each time he's left the diary out and I've looked through it a couple of times. Only the last time there was a new entry.
There's a picture of my grandad having sex with a girl I know. He's fucking her from behind, but the picture is from the side and she's looking directly into the camera.
Under the picture is a comment, and it reads "Wish this was Leanne".

What I've not mentioned yet, is I took picture on my phone, of the picture in the diary of my fifty six year old grandad holding his erect cock. And I've masturbated lots of times while looking at it, and imagining him fucking me with it.

I know I shouldn't think things like that, but it's difficult not to want him, as he's so sexy as a man.

What's more, is I've always been attracted to older men, and have had two boyfriend's in their late thirties. And a one night stand with a married forty plus year old.

It's clear we both want each other sexually, yet we're not supposed to. Next week when I stay over, I'm going to see what my grandads reaction is, to me being naked and horny in his presence.