The biological parents want to recognize their daughter who has been abandoned for 20 years. What can biological parents say to impress their children to recognize their parents?

This is absolutely unacceptable to anyone at the moment. Hate you can understand. Give her some time, don't be too eager to recognize, and influence her with love. After all, flesh and blood are dear to each other, touch her with your love. Over time, she won't hate you. Don't be too hasty This must be remembered, don't always mention it. It is pure kindness to her, and she will feel it. I have such an example around me. At first, it was dead, and finally the family had a good time. Use time and feelings to influence everything! Finally, I hope that one day you will be very happy together.