After 48 to 72 hours the fam leader should be able to just designate which of the inactive's planets are handed-over to which family member, along with fleet, science points, etc.
The planets should get handed-over with defenses and infra (including portals).
If you wanted to have some fun with this, since you would be creating the code for this hand-over, why not create a new op with it?
Call it 'orchestrate coup'. It could only be successful on empires of players who have not logged in for more than 24 hours. Or maybe you could make it doable on active players too? Instigate coup would have to be a very difficult op, and maybe unique only to one of the races. If successful, it would allow the opper to have a certain percentage of the targets empire's planets (including a certain percentage of their fleet, science points, infra, resources, etc.) simply handed-over to them.
Suddenly, the opper could gain ported planets in enemy systems. For this reason, the op should be very difficult, and usually only work to get 1 or maybe 2 planets, but, potentially, if the opper's agents / nw ratio is very much in their favor and if the target empire has been inactive for a very long time, the opper could get a very significant number of planets, fleet, etc., maybe even as much as 30%. You could make the probability of success of the op and the percentage of planets, fleet, science points, etc. to be handed-over greater the longer the target player has not logged-in. So, if the fam does nothing about their distributing their inactive players' planets, fleet, etc. among themselves, another fam could get it. 
You could also use a variation of this code to allow selling of planets, fleet, science points, etc, on market.