Betrayed Spouse here. (No stop sign). I will try and respond compassionately without judgment.
First off, you may want to put up a stop sign if you prefer Wayward feedback.
I believe you’ve come to the best place on the WWW for advice. The Posters here in this section are excellent. There are many wise and experienced Ex Waywards who post here who have impressive insight and clarity of thought. They should be able to help you healthfully reframe and get priorities in order.
Currently, you’re most likely a hot mess of conflicting emerging and latent emotions for BS, for AP, all meshing together with new and powerful maternal emotions.
I would first make sure that you’re in good safe environment. I would do everything possible to reduce stress and avoid acrimony. This should include full disclosure, honesty and transparency with everyone involved including yourself. Above all be honest with yourself. If your husband becomes abusive/violent or overly emotional, to a degree it is harmful to the babies, find safe refuge. Safe refuge in a neutral environment (Not with the AP) until things cool off.
Your priorities should be:
-Your safety. Fetal safety. Ensure your OB is aware of your situation and the stress you are currently under.
-Full disclosure and transparency
-Support BS from a position of safety.
-Stop the Affair. You are still married. Affairs are toxic and stress inducing to you, your babies, and your husband. Your AP should understand this. If he cares about your well-being he should back off. Get his identification then go NC. Does your AP deserve to know how you’re progressing through the pregnancy? If you’re considering R, I would work that out with your husband if it becomes an issue. Otherwise, I’d ensure NC.
-Be absolutely honest with yourself and your husband and the AP.
-Don’t try and manipulate AP or BS to achieve a certain desired outcome.
-Get a good IC who specializes in infidelity.
-Get an attorney if D is on the table.
-Do some serious soul searching with the help of an IC to find your path through this, to find your Why, and to find out what you truly want and need going forward. Your attorney, OB and your IC will guide you through this.
-Establish Paternity as soon as safe. One of these men will become a Co-Parent to some degree. Establishing paternity and processing the truth of the A will help your BS decide his fate.
-Be extremely careful about your co-parenting plan. I would not pursue or sustain a romantic relationship with anyone you are not truly in-love with just because you think they might be a good father. Don’t make concessions regarding true love just to facilitate a co-parenting relationship. If you conclude that you’re not sufficiently in a mutually loving relationship with either your husband or your AP, then pursue a loving relationship with yourself until the time is right, until you’re all right, and until the right man comes along and you and your IC conclude that you are a safe life partner.
-Children need to be raised in a wholesome, stable, loving environment. If your AP, husband or future significant other can not help maintain this nurturing environment then raise your babies alone in an environment you have control over with co-parent involvement to a degree that helps maintain this environment.
-I would not try and R just for the sake of raising the twins. Children will be adversely affected by false R, by any toxicity in your relationship. I would pursue genuine R or an amicable D.
-I would be VERY cautious pursuing a definitive romantic relationship borne from an A with your AP. If your AP is the father then pursue a non-romantic co-parenting relationship. Anything more is very risky. Whatever sort of relationship you pursue with the father, it should be genuine, based on honesty and provide for a healthy nurturing environment.