How many people cohabit though and don't have children? I see no reason why people without children should inherit in what might be a casual relationship.
In a case where there are no wills and there are children the childen inherit, which is the right thing.
In a case where a person (male or female) makes a will and refuses to leave their assets to their children, then I would conclude that the person is a right bastard, and clearly does not have the interests of their family at heart. This must be pretty rare though, and I am not convinced that such wide legislation should be brought in which will affect so many people, just to ctach a few right bastards, who are also keen enough in their bastardness to make a will.
In most serious cohabiting relationships the main asset is usually a property which is jointly owned - the co-owner gets the other half on dying. In the event that one partner has refused to allow the other on the deeds then the right bastard thing kicks in again.
Most company pensions etc now include cohabiting partners as beneficiaries, so that is OK.
Financial difficulties often come from not having life insurance etc, which applies just as much to married as cohabiting people.
I am not at all convinced that this is a feminist issue. I think it is a right bastard/sledgehammer to crack a nut issue.