grand children

Can't make a judgement about this - not enough information.

Some children are still impulsive at this age - especially if overexcited/hyped up on sugar around Christmas. Some children have special needs and can behave younger than their actual age

In general definitely not.

But some children have conditions which cause them to react violently or unpredictability.

You definitely can’t make a judgement on one sentence

I would want to have much much more information about the event before I reached any judgement.

The answer could go either way depending on the circumstances.

no never it is only one of their children a seven year old who does this, to both his mum and dad

There may be a reason for their bad behaviour.

No . Do the parents lash out at the children?