I haven't been in your shoes so I can't relate to your situation 100 percent, but any stepchild would be lucky to have you as a parent. I am a child of divorce and can speak to that.
But since you technically don't have legal claim to those children, you will likely have to wait things out until they get to an age where they can reach out to you.
Until then, have you considered finding other ways to connect with children in a way that might be fulfilling for you? It may not replace being a parent, but there are several organizations that are in dire need of adult volunteers to help kids who may lack parental support in their own homes. Or, organizations like the Boys and Girls Club or Big Brothers, Big Sisters could provide a mentorship opportunity for you if you have a lot of love to give.
Beyond that, if you want to be a parent again, maybe sponsoring a foreign exchange student might be something for you to consider. If you're in a place emotionally or financially where you could be a foster parent, that could also be an option. I hope things get better for you.