They may be "1/2 siblings", but he adopted the 7 year old and as far as I am concerned, that makes her his daughter. Unless you are saying she isn't as equal as his biological daugther is. Just wondering if you missed that fact that he adopted the 7 year old.
I certainly don't feel it is fair that the adopted child be made to feel like she isn't as loved as her sibling. That is not only sad, but cruel. The time for him to have decided how he was going to feel about this child was before he adopted her.
Before you jump all over me, I adopted a child with my 2nd husband. We had spent 5 1/2 years doing infertility treatments, with lots of money and 3 miscarriages. We decided it wasn't going to happen for us. We adopted a lovely 8 year old, who was actually related to me. Her Mom was my 1st counsin and had died when her daughter was 5 years old. She was being raised by her grandparents, my aunt and uncle.
We ended up discovering just as we got started with the adoption process that I was pregnant. We discussed if we should go forward with the adoption, and we both said "We have enough love for 2 children."
Once she joined our family, I never thought of her as anything more than our daughter. She had our name and our son, was her brother.
When my former husband died, she was entitled to 1/2 his estate, as she is considered by law, to be a legal heir.
This 7 year old is entitled to the same consideration and love and attention, as her 4 year old sister. He adopted her and by doing so, said "She is my daughter." He doesn't get to change his mind now and just claim his biological daughter is his true child.
I agree with Jada. By his adopting the 7 year old, he made it a package deal, and he doesn't get to pick and choose now.