If your mom caught you sucking your thumb, don't be too embarrassed. First, try to understand why you still have this habit. It could be for comfort. You can talk to your mom about how you want to stop. She might be able to help you by reminding you gently when she sees you doing it. You could also try using a substitute like a stress ball to keep your hands busy.
Definitely not. Sharing something like that with a sister is highly unethical. Family relationships are based on respect, love, and appropriate boundaries. This kind of sharing violates those boundaries and can cause discomfort, harm to the relationship, and is not acceptable in a civilized family environment.
No. Such a situation is highly unethical and goes against the principles of loyalty and respect in a relationship. It involves inappropriate and disrespectful behavior towards one's spouse and violates the boundaries of a committed relationship.