Sister's affair

[madasa]

Hi am hoping for some advice so that I don't start a massive fallout with my sister.
Background which I will try to keep brief:
My sister has been with her DP for 20 years. Two children age 12 and 15.

They have always seemed to have a solid and happy relationship.
About a year ago things started to change. They were arguing a lot and she told me he was not wanting her to go out etc. etc. and she wasn't going to live like that.

A man's name was dropped into the conversation several times and suspicions began to form in my mind.

Fast forward to a couple of months ago. She has bought a new house with inheritance from my dear dad who died two years ago.

Flowers from this man (a work colleague) turned up at the house even though he was living with his partner.

Suffice to say she told me a couple of weeks ago that she had met someone. To her surprise I told her I already knew, told her his name and told her that in my opinion it had been going on for a lot longer ie. whilst she was still with her DP.

I know that it is none of my business and have agreed not to discuss the situation but that I am not a fool and that none of what she is saying adds up.

Now I have the situation re Xmas. We are staying at home and I have told her she and the children are more than welcome.

She has just asked if this man can come too. AIBU to not want to share my Xmas with this man that was cheating on his own partner whilst my sister was cheating on hers? I just cannot sit there playing happy families.

My sister has lied to me and also to her DP.
It's not the fact that she has someone else....relationships break up, life goes on. It's all the lies and deceit that have been going on.

Any ideas on how to reply to the text asking if he can come? (without using the words cheating and bastard!)
I don't want to fall out with her and I love her dearly but I just don't recognise her at the moment.

Thanks for any help

I don't know Mad but my ds did the same I spose she thought it was just a fling and it would soon be over or perhaps she was hedging her bets if it didn't work out with lover boy then stay with dh?

I guess there are all sorts of reasons guiltyconscience

Sometimes people stay in a bad marriage because they lack the confidence to leave and start again alone.

True

Well I think maybe her relationship wasn't absolutely horrible, but when the new man came along, he swept her off her feet. And she wouldn't have left immediately, because she needed to build a relationship with the new man first. Otherwise she would have risked destroying her relationship for nothing (as GC says). In my sister's case, she was waiting until she thought her kids were old enough - ie through school.

What happens, ime, is you just get led by the nose from lie to lie to lie. Your life suddenly becomes so exciting and all-consuming that you put it first, second and last and other people are just obstacles to your complete happiness!

It's very selfish of course, but to the people concerned, it almost feels as if you are fighting for survival. I think.