My sister stayed to watch an old story. What could be the reasons for her to be so interested in it?

Talking in sleep can be caused by various factors. It could be due to stress. For example, if she has a lot of schoolwork or is facing some problems among friends, it might show up as sleep - talking. Another reason could be irregular sleep patterns. If she doesn't have a regular bedtime or wakes up frequently during the night, it can disrupt her sleep cycle and lead to sleep - talking.

Well, perhaps the sister is really into fashion and wants to experiment with different looks on someone, and her brother is the most accessible model. Or she could be preparing for a school play or a local theater production where she needs to practice dressing a male as a female character. Maybe she just wants to break the gender norms in a fun and harmless way within the family environment. It could also be that she's trying to teach her brother about empathy towards the opposite gender by making him experience what it's like to be dressed as a girl for a while.

It might be due to a competition. For example, if they are both into the same sport or activity and there was a limited opportunity. Say, only one could represent their school in a tennis match, and they started fighting over who should be the one. They could have said mean things to each other which led to a full - on catfight.

She might be in pain. Maybe she has a headache, a stomachache or some other physical discomfort. Check if she needs medical attention.

Well, it could be that mom is feeling lonely or her own children are growing up and leaving home. So she wants her sister to have a baby to bring back that sense of family togetherness. It could also be that she sees her sister as a great potential mother and thinks a baby would complete her sister's life. However, these are still mom's own projections and not valid reasons to force the sister into pregnancy.

One reason could be that the little brother has been disobedient. For instance, if he was told not to play with a certain dangerous item but did it anyway. Another reason might be that he has been unkind to others, like bullying a younger sibling or a neighbor kid, and the sister feels it's her responsibility to correct his behavior.

She can learn about different animals' behaviors. For example, if it's a story about lions, she can know how they hunt and live in groups.

Jealousy could be a reason. Maybe one sister was jealous of the other's popularity or the attention she got from others.

Maybe she loves cats and her sister has some really interesting cat stories to tell. It could also be that the way her sister tells the stories is engaging.

One possible reason could be that the sister has some sort of psychological issue. Maybe she always wanted a sister and is trying to create that ideal situation in her own way. For example, she might be lonely and think that having a 'female' brother would make her feel better. Another reason could be related to some family pressure or family dynamic. If the family has a history of valuing femininity more, she might be trying to fit her brother into that mold to gain more family approval.