This legend could be shown at the end of the existing Info/Help popup window narrative or, perhaps better, on a separate popup list initiated from the click of a new small icon. This legend should not, of course, be restricted to the ERs line types but also show all others, e.g. divorce line, cohab lines, etc.
I 'd like to point out that, as far as the Social Relationships (SR) are concerned, the make up/display of a SR legend could be a problem because the line type of a SR is user selectable.
Thank you