Polygamous, time limited civil partnerships
Since it is now usual for 2 people in a marriage or civil partnership to work, it has raised the bar so that 2 people prettymuch have to work.
If you have children then this creates a problem of neglect – what is needed is someone to stay at home.
If you had 3 people in your partnership then either one could stay at home or work shifts can be arranged so the child can be better looked after.
But it doesn't just apply to when a child is involved – some people would like so say that they are financially tied to each other and eg. want the rights of a spouse in a hospital or just to show their love to the ones closest to them.
So I suggest that people should be able to form a partnership with anyone they like and any number of people. Perhaps not call it marriage as that comes with too much baggage.
This partnership should be time-limited at the start for perhaps 20 years at which point it can be renewed, or if there is a serious problem before this time then a "divorce" is possible but shouldn't be easy.
Some restrictions would be needed to ensure dangerous cults are not created or that people are not forced into this. Also if the partners are closely related this doesn't give them any more right to biologically create children given the likelyhood of defects.
Of course those wishing to go for their "Till death us do part" marriage is perfectly OK still.
Why does this idea matter?
Both rights and responsibilities are available to anyone, whatever their view on life or relationship arrangement.
Updates the partnership rules to be pragmatic to 21st century life.