You will need to make sure this is written as a clearly arguable question. Here are some possibilities:
"Should a rapist have parental rights to a child born from the rape?"
"Is there a situation when a rapist deserves to have parental rights to a child born from the crime?"
When I first read your question, I assumed most people would argue that no rapist has any right to demand anything. However, I thought about some instances where a prior relationship between the two people involved which might make this a question that could be argued. One situation is a rape of a wife by her husband, or a rape between a couple living together or two people in a long-term relationship.