From 2003 study:
1parent bipolar 1 not: 15-30%; 2 parents 50-75%; 1 child with, 2nd child 15-25%; 1 id twin with, 2nd id twin 85%.
But figres like this do not take into account the cross inheritance of other mood disorders
and rarely discriminate fully between bpd
i and ii.(but i and ii is an important distinction for you).