How to tell my daughter she’s adopted (“step parent”)

I’m an adoptee, closed adoption. My family never kept my adoption from me. It was normalized and open for discussion. Be open, tell your child the truth. The sooner the better. Explain her biological father was not equipped to care for her in the way she needed to be, but you were. During that time, explain you met a stable loving partner who not only loved you but also your child. Once you married, he asked if he could adopt her as his own. If she asks questions about her father and bio family on that side, try your best to answer and support her need for answers.