it's quite unlikely that faction leader wouldn't have children...

but you could give faction leader of faction 'c' trait 'a' (I think)
and give any children of that father with fathertrait 'a' another trait 'b'

and then set condition in script that if no-one living has trait 'b' all of faction 'c'
is given to faction 'd'

am not entirely sure if the link to princess is recordable - you'd need to work out
if marriage of princess from faction 'd' can be used in first place to trigger giving trait 'a' to leader of faction 'c'


if you've only got two factions the example would be as above - if you've got a lot of factions the whole thing would expand exponentially, with you needing to code each case; eg. that princess from faction 'f' marries leader of faction 'g', or faction 'd' etc... and every other permutation!