when we want to find out about other persons in a chart we count from a Bhava. should we count Rashis or House cusps.
For example; father in Law is 10th from 7th, which will be the 4th, but is it the 10th rashi from the 7th cusp, or the 10th house cusp from the 7th cusp
I've always learned Bhavat Bhavam rasi to rasi (full house to full house) but Ernst might have a different technique and look directly at the cusp (4th cusp for mom, etc...).
For this we count rasis if I've not been completely asleep in these classes. These are not "concrete manifestations", those are more like yoga. Hmm... let's see what Mr E himself had to say about it...
I am looking at the house cusp if I want to read about the younger sibling's body and their life, so I look at the 3rd cusp.
If I want to read the person's relation to the sibling, I look at the 3rd rasi.