Why did the parents decide to talk to the twins? (Understanding)

The two feelings the twins experienced after using the tablet too much were tiredness and grumpinsess.

The twins promised their parents not to use the tablet without their permission.

The home became full of joy because the children started playing outside with their friends again. Also, the family members used to sit together every weekend and shared funny stories.

I would make the dinner table a "No-Tablet Zone". In the text, the family became happy when they sat together and shared stories. If everyone is lookinig at a screen during dinner, they cannot look at each other's face or hear funny stories about their day.

The tablet usage caused the children to feel sleepy all day long because they couldn't sleep properly at night.