Yes it is OK for you to express your anger and frustration, but it would be even more meaningful for you to do what you are hoping he will do: act. I’m sure he has talked to his daughters, but it hasn’t brought about change. You might have to lead by example and show some tough love. In other words, as much as you don’t want to end things with him, doing just that might be the incentive he needs to really lay down the law with his very adult children.
However, you also need to really ask yourself what you are willing to live with and what you are not. Do you love him unconditionally enough to allow for this situation to go on indefinitely or will it only build resentment if he never puts good boundaries in place with them, whether or not they live with you? Leaving him now would be easier than leaving him down the road, especially considering the circumstances of the daughter with Bipolar Disorder and a young child. Are you willing to let them come in and out of your lives? There are no right or wrong answers. I just want you to think about how you want your life to look. Many times, love just isn’t enough.
It might be helpful for you and your fiancé to engage in some couple’s counseling. Or at a minimum, read some books together on boundaries and codependency. I hope you can find a mutually agreeable solution.
All the best,
Dr. Holly Counts