Equal split. But a child should die, there ‘split’ should go to their family - partner/spouse/children.
Yes, definitely this. You shouldn't lose out twice just because your parent(s) dies young.
My sister and I stand to inherit everything between us from our (widowed) DGM, as both of her DSs and her DIL predeceased her, our DU sadly as a very young child. However, had he lived another 20 or so years and been in a position to have married and/or fathered children himself, we would most definitely expect/have expected his wife and/or child(ren) to have inherited their DH's/DF's share, irrespective of whether our own DF had pre-deceased his parents by far fewer years than his younger DB or indeed outlived them.
Interestingly enough, we know a (now-deceased) widowed DF/DGF who had three sons:
A - single and with no children;
B - married with two children;
C - married with two children.
When planning and discussing his will, the DF/DGF believed it fairest to split his estate 9 ways - 1/9 to each son, wife and grandchild.
Son A agreed with him, had no issues at all with this and was very happy to receive his 1/9 share.
Son B was happy with this, but thought it would be fairer to split it three ways between each family/unit, so that Son A wasn't penalised purely for never having married or had children.
Son C was very unhappy because, although his own family would receive 4/9 (i.e. more than a third) of the money, he protested that it should be split three ways, because he wanted 'his' whole third to himself rather than having to share more than 'his' third with his own wife and children.