I was just going to post exactly the same point! A bit more education about their rights for the minority of people who don't understand that co-habitation does not confer rights that marriage or civil partnerships do- that's all the government needs to do here! Forcing everyone else to make major adjustments to their lives is, to say the least, a very odd way of doing things.
(BTW, remind you of anything else we've been discussing here for more than a decade?)
I am assuming that, if they go ahead with proposals, they will need to "equalize " IHT laws to include these new legal co-habitors? That would actually mean they would get less IHT upfront from each, formerly "single" person, because, as PP said, there is no IHT due if you leave everything to a "spouse." (I think that's right?).
I have been married twice, but am now a widow. I have no plans to ever live with anyone else again, but if I decided to do that, no way would I let any new partner or partner's adult children (likely to be in their forties or fifties) inherit everything I've had from my grandparents, parents, and late husband.
I can't understand the government's thinking on this.