What should one do if someone tries to tell 'first time i played with his penis stories'?

No, it is not appropriate at all. Such topics involve private and inappropriate sexual content which should not be shared or discussed in public or general conversations.

First, the person being blackmailed (the mom) should not give in to the blackmailer. Then, she should consider involving the authorities like the police. It is important to stop such unethical behavior right away.

One should firmly resist the blackmailer. Don't be afraid of their threats. It's important to preserve any evidence of the blackmail. Seek professional help if needed, such as consulting a lawyer or a counselor. The law is on your side in such cases, and the blackmailer should be held accountable for their actions.

The sister should report the situation to the authorities. Blackmail is a crime in many places. At the same time, she should surround herself with a support system, such as family and close friends. They can help her stay strong and not be intimidated by the blackmailer. Also, she should avoid any further contact with the blackmailer if possible.

Politely ask them to stop. Such stories are not suitable for public sharing.

Stop them immediately. It's not acceptable content to be shared.

You need to protect your mom. Let her know she doesn't have to comply with the blackmailer's demands. Try to figure out who the blackmailer is. If it's someone you know, you might try to have a conversation with them to stop this unethical behavior. If that doesn't work, seek legal help.

Politely stop them. Just say that this is an inappropriate topic and you don't want to hear it.

Tell them clearly that this kind of story is unacceptable and disrespectful to your family. If they continue, you may need to distance yourself from them as they lack basic respect for boundaries. Also, you might consider reporting their inappropriate behavior if it persists and makes you feel harassed.

Tell your mom not to respond to the blackmailer at all. Keep any evidence if there is any, like messages or emails. You can also seek legal advice. Maybe consult a lawyer who can guide you on how to handle the situation legally and protect your mom's rights and reputation.