Distinguishing scattered Compton electron in Force Collision biasing


how can I distinguish the first scattered Compton electron from the second scattered Compton electron in Force Collision biasing? for scoring their energy deposit at each step in biasing.

I checked the parent id of produced electrons and their track id from 1 collision
it seems that when I use biasing, the parent id of the primary Compton electron is increased by one relative to without using biasing.

I found that primary electrons produced have different track id so I can’t track them by their track-id and parent id. (i tracked primary electron produced by checking where the track is created using the GetVertexPosition() method.) please correct me if i am wrong

so how can I distinguish Compton electrons? I think all of them have parent id equal to 2.