Thunks, I'm not sure I understand what you mean. If a random stranger killed a man and his children, the grandparents would have lost all their grandchildren (presuming they had no others, not that that would make it any easier of course.) If a man kills his children and then himself, the grandparents have still lost all their grandchildren.
The point has been made many times on this thread, with references to external sources, that the context and pathology of men who kill their children and/or partners then themselves involves an extreme extension of their sense of male entitlement. They often have a documented history of abusive and/or controlling behaviour related to their partner and children, effectively regarding them as something they "own," and killing them is the ultimate expression of their sense that they are entitled to control them.
When strangers or acquaintances kill families, the context and motivation is very different. Even when mothers kill their children then themselves (and as pointed out, murder/suicides perpetrated by women are very rare,) the context is very different.
The other recurring issue is how the media "treats" such stories very differently from stories where the killer isn't the father, unless the father fits a popular stereotype of "undesirable" (e.g. criminal record for offences against people other than his family, immigrant, from a minority ethnic group, long term unemployed, that sort of thing.) The press works out who are the "goodies" and the "baddies," and when a person does something that doesn't fit the stereotype (i.e. father kills his kids,) media reports seem to go overboard with boosting up his positive side while at the same time pointing the finger of blame at the mother, even if she's also been murdered.
And yes edam, in its simplest form, that's what it is, obviously, with all the context stripped away.