Is it okay to have fantasies about my little sister she is 11 and i am 15

It's important to acknowledge that having feelings or thoughts about a sibling, especially when that sibling is significantly younger, can be complicated and may not be appropriate. It's essential to focus on healthy and supportive relationships within your family. If you're struggling with these thoughts, it may be helpful to talk to a trusted adult or a mental health professional who can provide guidance and support. Prioritizing well-being and boundaries in relationships is key.