My grand daughter used to have terrible "meltdowns", often for the most trivial of reasons, or even no discernible reason at all. She would become uncontrollably angry and distraught and nothing whatever would calm her down.
I read a book called Love Bombing which I found quite useful. Although some of the writer's suggestions seemed a bit extreme to me, I took from it the need for demonstrations of closeness and love, both through actions and words.
My grand daughter (touch wood) doesn't seem to get these bouts of prolonged crying very often now but when she does become angry/distressed I give her a great big hug rather than try to reason with her. In fact, every time I see her - and her brother - they remind me that we must have our "great big hug".
My daughter tells me that I was very undemonstrative and not at all tactile when she was little - and, on reflection, I can see that what she says is true. She has had her problems over the years and I can now see that the lack of hugs, combined with an over-critical parenting style, has been a contributing factor.
I'm not saying the problem with your grandson is a parenting issue - I'm just relating my own experience. Even if you had given more information, I don't know your family or how they respond to each other. It may well be, as absent says, that this is just an extreme case of the terrible twos/threes and the tantrums will eventually disappear. Perhaps very young children who cannot express themselves well verbally can feel suddenly overwhelmed by their feelings. Anyway, I don't think more big hugs and affectionate words will do any harm.