Helen7
LostCousins Superstar
If you put just a surname in 'Other household member' you get far more hits than if you put the forename as well. Likewise if you just put a forename and leave out the surname, you get far more hits than if you include both names. So it seems to me it is matching on both forename and surname, rather than either/or.you might inadvertently include someone in another household if you're not careful as the 'Other household member' boxes do NOT match on both forename and surname, only on one or the other.
I agree that if the 'Other household member' has a common forename and surname, you could well get other households too, so caution is needed in such circumstances.