How common/uncommon is it for a seven year old child to have thoughts of being dead?

Those thoughts being: the wish to not be alive anymore and then I wouldn’t be a burden for you anymore.
This is a true ‘case’ about which I would rather not give more information than that what I stated above.
I only will say that this is dealt with thoroughly.
My only question here is whether you know (first hand or second hand) if this a (un)common thing to happen in such young children?
I know from myself that I didn’t have these thoughts, not before the age of about fifteen or sixteen.