To exclude my sisters married boyfriend

[possum18]

Just over a year ago my sister started sleeping with her much older boss, who was married to his pregnant wife (she was around 2/3 months pregnant when it started) whom he shared two other children with. Their affair came to light shortly before the third child was born and the wife was left to give birth and care for a new born and two young kids alone whilst my sister and her boyfriend went on holidays..etc.

My parents are very hurt by her actions and want nothing to do with her boyfriend, and have very little to do with my sister now.
They are moving in with one another this weekend, and all of a sudden my sister has become a lot more open about their relationship around me and our parents and has told us all that we are to be supportive and inclusive of her and her new life. She sent me a picture with herself and his children and captioned it 'happy families' and I didn't know what to say. I think what they did to his pregnant wife is disgusting.
I'm very heavily pregnant (and hormonal) and would like my sister to be involved in my life, but really want nothing to do with her boyfriend, who is still married.

My parents are trying keep civil as my very elderly grandparents would be devastated if they were ever to find out what my sister has been up to.

I don't want my sister to feel excluded but I don't know how to go about having her involved heavily in my life and new family whilst wanting nothing to do with her partner and his kids.

Any advise would be great fully received!!

I expected this has been said already, but if you are disgusted by their relationship then how can you carry on with your sister? Presumably we all have lines we cannot cross.

Some things are black and white to me. Fucking someone else while ttc with your wife is plain wrong. Fucking someone who is married and having a baby with his wife is plain wrong. I judge that whether I know the people concerned or not. Perhaps the OP is choosy about her friends iyamehooru and expects them to have some morals.

You must set boundaries with your sister, imho, she is using you, playing on your sisterly love. It was not you who put yourself in an awkward situation, but her. Therefore, I guess there would not be any moving forward without an open talk or a letter, if you prefer to set this in writing. Firstly, try to establish what is important to you and what is an absolute no-no. Secondly, try to imagine what would happen should you accept/cut off. It might be that if you accept this boyfriend of hers they would expect you to accept many other things for which you are unprepared. You sister might, of course, ignore your attempt to place things clear. This is why your conversation or letter should be very firm, I am afraid. I have been in similar situation, although it was not entirely your setting. I have to say it is impudently unfair to expect your relatives to carry on as if nothing happened, disregard their feelings and then demand consolation if things go wrong. I have found it selfish beyond belief. You can communicate with your sister about your baby, your life, etc without her bringing her boyfriend into conversation. If she is there for you - she would agree. Time will tell whether her relationship will be a solid one and she must accept this, rather than barge in demanding acceptance. The same goes for her boyfriend. If he is a decent man who found no other way out of unhappy marriage but to make 3 kids first and then dump his wife whilst she was pregnant, there must be a very good reason indeed. Or he is a disgusting weakling with no morals or responsibility. In any case, he must know how this looks to any decent person and accept that for a certain time he would not be welcomed. He is not your sister's husband so why there should be any acceptance at all? Love is also giving an honest opinion on your fears and attitude towards the whole situation. Love means to be free from obligation to communicate to someone who is just a lover of your sister. Respecting yourself might make you sister take off her tinted glasses or realize that unconditional love is reserved for babies and kids, adults suppose to behave.