We're here
I get the feeling of how hard it is to wait for the next counseling session. That's one of the reasons I post here -- life doesn't wait for a good time for you to have support lined up, it just hits you with all kinds of heavy stuff at inopportune moments. So, yeah, we're here.
In terms of the kids, even though they are adults, I'd go slow and not hope that they will "join with you" right away. You will probably need to do more of the lifting in those relationships for a bit. If you do want to test the waters down the road (I wouldn't do it right now right as you are learning about BPD), you may need to do it from a "secure, stable father" place, where you can be the one they lean on as they process stuff about their mom.
One way to broach the subject is with a general statement of "as time goes on and we get older, sometimes we have new insights about our families and the past. If there's ever anything you want to ask me about when you were kids, or me or mom, please know you can do that whenever you want".
That let's them know they don't have to talk about stuff or share your position, but that you want to support them wherever they are at. That is really important to "stay the dad" because in many families where a parent has BPD, the family structure gets "inverted" and one or more kids "become the parent" to the pwBPD -- taking care of their feelings, putting the parent's needs first, etc, instead of the parent doing that for the child.
Basically you also want to avoid "trying to get the kids to take your side" as that is "more of the same". Now that you have new info about BPD, and can check out the links on this site about the impacts of a BPD parent on kids, you will be well equipped to listen to and be supportive of your adult kids (vs what a BPD parent would do, enlist them to take a side).
Over time, as your kids see that they can trust you as they talk about their experiences with Mom, you guys may have more "equals on common ground" talks. But for starters, I'd lean towards a LOT of listening. It'll pay off.
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What's something you've learned about BPD that was a huge "lightbulb moment" for you? What do you most want to dialogue about?
