Jack and his brother, Jay, were teasers.

[alpacinou]

Is this correct and natural?

Jack and his brother, Jay, were teasers. They would never miss a chance to mess with their mom. One day, she took them to a friend's garden. There was a raspberry bush at the corner of the garden. Jay picked a ripe raspberry and squeezed it until his hand became scarlet red with the juice of the fruit. Running towards his mom, he screamed, Blood! Blood! My hand is bleeding mom. Nicole stared at her son, open-mouthed, fumbling for her phone to call the emergency service. "Gotcha!," said Jay, he and his brother falling on the floor with laughter, their hands on their bellies.

I'm concerned about the underlined parts and I would appreciate it if you would make suggestions for me to make them better.

 

[Charlie Bernstein]

It's fine as long as he doesn't mind wiping raspberry juice on his shirt!

 

[Tarheel]

I thought they were outside. Why would they be falling on the floor with laughter? (Falling on the ground maybe.)

I don't know that it's totally believable. Considering that she's their mother, she's probably used to their hijinks.

Overall, it's OK.

 

[Tdol]

You could say that his hand ran red with the juice.