Well, in the 'big mom is luffy's mom fanfic', they might have crafted a story where Big Mom is Luffy's mom. But it goes against what we know from the official 'One Piece' story. Fanfictions like this can be really interesting as they can rewrite the story in unexpected ways. They might have some interesting plot twists and explanations within the fanfic to justify this relationship, but it's not part of the main 'One Piece' universe.
One possible plot implication could be a change in Luffy's power source. Since Big Mom has such unique and powerful abilities, Luffy might inherit or be related to some of those powers in the fanfic. Maybe his Devil Fruit ability could be related to Big Mom's in some way.
A mom can start by giving the child a big hug. Physical contact often makes a child feel safe immediately. She can then ask the child what's wrong in a calm and soothing voice.
One story could be about a time when you were stuck in a group project at school. Mom might say to pull out your best communication skills, like she once told you the story of how she overcame a similar teamwork issue by being open and listening to others. So, you start actively listening to your group members' ideas and communicate your own clearly, and that helps you pull out of the potential chaos of the project.
First of all, don't be swayed by any possible justifications she might give. Reject the request immediately. Consider having an open and honest conversation with a trusted friend outside the family about what's going on. They may be able to give you some objective advice on how to handle this difficult situation. You could also look into local resources for family support or ethical guidance.
Perhaps Mom told a story about a time when she had an argument with a friend. She pulled out her ability to forgive. She realized that holding a grudge only made her feel worse. So when you're feeling down because of a conflict with someone, you can think of this story and try to forgive, which can make you feel better and pull you out of that negative mood.
It might mean that the end of mom's siblings is related to telling stories. Maybe they are in a situation where they are concluding their lives by sharing their life stories.