Laurie , through many years with my older daughter , it was hell. I didnt know i had ptsd and went from one disaster to the next. But somehow i held onto her and tried to do whatever i could and most times it was never enough. For many years she almost hated me but at the same time still wanted to spend time with me and i don't have many fond memories of our time together. It seemed she was put on this earth to give me a hard time. Slowly over time we were able to repair the bonds , it wasnt something that happened quickly but rather over many years. But through all of this she understood that she could come to me with anything, any problem and i would never judge but simply help her. We know have a solid relationship.
Dont give up mate , they are your offspring and that biological connection is far stronger than you realise. You may not get your time now , but you will get it , that you can almost be assured of. Dont give up and rather plan for the day when they're not under the guise of the other parent but their own people, free to make their own decisions, and they will return and they will want to know you , please be patient and dont give up hope.