In most jurisdictions, having a baby with a close blood relative, such as a sister, is considered incest and is illegal. Furthermore, such relationships can lead to severe genetic risks for the child due to the potential for increased genetic abnormalities and inherited disorders resulting from a shared genetic background.
The laws and social norms surrounding incest vary by country and region, so it's essential to consult legal professionals to understand the specific regulations in your area. Regardless of the legality, it's crucial to prioritize the well-being of any potential child and consider the potential risks and ethical concerns involved in such situations.
If you have concerns about family relationships or are facing complex ethical questions, it's always best to seek advice from a licensed counselor, therapist, or other qualified professionals who can offer guidance and support tailored to your situation.