to tell DS the truth about why he can't stay at his cousins?

[iceandsliceplease]

I suspect IAB deeply, deeply, U, so perhaps I want you to talk me out of this, but...
Very long back story here, which I'll try to skip as much as possible. DS (6)& his cousin (also 6) are and always have been very, very close. DP, my brother, SIL & I ran a business together, so shared childcare. 18 months ago, I had a pretty catastrophic nervous breakdown, numerous suicide attempts, was generally in a very bad place (mainly due to pressure from work, and lack of support/bullying from brother & SIL). We left work, moved away, but tried to keep up the relationship between DS & DN as much as possible.
Brother & SIL had no real contact with DP & I, but it all got very messy, with legal action against me. My sister fell out with brother and SIL, my dad no longer speaks to brother & SIL, my mum...it's complicated... Brother & SIL have now sold the business and moved ten minutes away from us.
We had, until fairly recently, still had DN to stay/play quite regularly. He stayed the night only 10 days ago. But more stuff has come out. I found out that SIL has told A LOT of people that the reason we moved was that I stole money from the business and did a runner. She's referred to my being sectioned as 'her little stunt'.
And now that my DN is so close, DS & DN are constantly badgering me to let DS go and stay at my brother's house. I DO NOT WANT DS STAYING IN THEIR HOUSE. So far, I've been very non-committal 'hmm, let me check my diary when I get home, no sorry, we're busy, can't I'm afraid.' DS isn't happy about it, and can't understand why I won't say yes, especially when my brother tells him 'of course you can stay any time you like'.
I wouldn't ever tell DS the full truth of what's gone on, but AIBU to explain that my brother & I have had a falling out, and that's why I don't want DS to stay? DS is a nosy child, so I would have to provide information of a vetted kind.

Blimey, what they did to you is horrible. How DARE they tell such lies!?

A1980 might be right, just say 'no' and don't discuss any further. But I'm not sure how long that will work - your nephew and ds might be friends for years, how long can you possibly keep up the pretence that everything's OK?

Can you not explain to DS that the grown-ups have fallen out? Surely he must have realised that much?
Then explain that because of that he and his cousin can play together but that you don't want him staying with adults that you don't get on with.
And basically (but nicely) that it's that or nothing?
And when he's older you can explain more fully.

I found saying 'trust me, it's something you won't understand now, I promise I will explain it fully when you are a bit older' surprisingly effective and acceptable to my dcs.

Given all that's happened i'm with you - I wouldn't let ds be with them without a third party to supervise.

When I was 7, I would have understood a falling out if my mother told me. In simple terms of course. I would continue to be evasive, and eventually tell him a mild condensed version.

Yes I agree with not letting him stay but just saying you've fallen out. If you go into detail he'll most likely repeat it to DN and it'll only make matters worse.

Feel so bad for you though, aren't some people absolute shits?

Agree with nannyogg, but would also be taking things in hand with sil now. I'd directly tell her that if she continues to lie about and generally bad mouth you to all and sundry, you will take legal action against her. She needs dropping and slapping back down to size or she will keep taking the Mickey.
Poor you OP, hope you can resolve all this and regain some self esteem and confidence to deal with sil.

I think you need to give him a very brief and honest explanation. Otherwise he will know something's wrong but won't know what. And that's a horrible feeling.

NannyOgg's version of what to say sounds very sensible. Could you say that you don't want to give details about why you've fallen out because it feels like too grown up a conversation. I think it's really important to be honest, but that doesn't mean you have to tell all.