I take it that you are saying, add a 'deselect ancestors' & 'deselect descendants' button to each person in the list. Because you can already deselect, by unchecking the individual name. Would not another option be, to add an invert button at the top and bottom of the list, to let you in one hit, select all the unselected ticks, and unselect all the selected ticks, in one button press. That way, you have the ability to go through selecting all your relatives, then invert your selection, to remove your non-relatives. Another option, would be to put some sort of icon next to each name, to indicate whether they are blood relatives, or connected to your tree, or unconnected from your tree. Difficulty is, once a profile is connected to the global tree, then you are connected. Perhaps another better option, is to put two numbers after the icons after each name, the first number to indicate the distance of a relative in steps, the second number to indicate the distance of a connection in steps. If they aren't a relative, place a - instead of the appropriate number. Likewise for connections, if not connected, at least within a set number of steps, show a dash -. The only problem with this is, it will potential burden the system, for all the extra calculations it will need to make, to show your entire list, with those extra details.
