Not according to the Law of the land they arent. Dont want the protection marriage gives you , fine, dont get married, want the protection? either go through hoops to get it or get married.
Very true.
You can't have it both ways.
Rather than wondering whether you are entiltled to a share of the home or not, I would advise anyone in the BFs position to get married or sort it out in another way legally.
It's all well and good wanting to label marriage as a prehistoric concept, but the truth is that it isn't. If you think it makes no difference, you can see how financially vulnerable you could be without the legal protection that comes with being married.
Just the same way you could be a SAHM, give up your career and if the marriage ends, you aren't entitled to spousal support or you start a legal battle to prove you were 'as good as married'. The law won't care much about how you view your relationship at this point.
If you cohabit, then you need to be very real about the implications for you, in the event of a split or death. This is especially important if you are not earning, the lower earner or do not have a joint mortgage.
If your home is in your boyfriend or girlfriend's name, if they die, their family can get you out of there.
Get better informed if marriage is not your thing, as you could find yourself up the creek without a paddle and that's the last thing you need when you've just lost a loved one.
OP - If for argument sake your sister was still in a relationship with him and she passed away, the house would go to your parents, or siblings. He would be viewed as a boyfriend and if he wanted any money, it would be a legal battle. He would have no automatic legal claim.
My friend was engaged and living with her fiancé. He died very suddenly and his family were quick to swoop in regarding his share of the house. Except my friend had a "joint tenants' mortgage and not 'tenants in common' one.
With the latter his share would go to his NOK. With the former it became hers automatically.
I don't see on what grounds the Ex wife would get a claim on anything - not that I actually think he should either, but even if he was on the mortgage it's nothing to do with his Ex as they are divorced. At least we think so.