I was a step granddaughter. My father never called me his step child and my grandparents never called me their step grandchild. When my cousin died at 88 several people asked who I was and when I said I was dad's daughter, Jo Ann, they said "Oh, but he only had two children." My dad was so upset and said no one will ever say that again, I will adopt you. I was adopted at 37 years of age. Oh how I loved my dad. I lost my birth dad when I was about 22 and my mom remarried when I was 12 so my step dad was my day most of my life and I always thought of him as my dad. He died in 1993 and my mom in 1988 and I still miss them. I hope your step great granddaughter can become your great granddaughter one day. God bless.