If I understand you well, you generated the electrons out side FairRoot, and then you transport them with FairRoot through your detector. i.e your electrons are considered as primary particles, so you can cut on the Mother ID of your points (it should be -1 for primaries). From your MCPoint you can get the TrackId of the track which generate this point (FairMCPoint::GetTrackID())and then the Stack you get the MCTrack and then the mother ID of the track.
motherID = (((FairMCTrack*)fMCTrackArray->At(FairMCPoint->GetTrackID()))->GetMotherId());
In the event display you can select display primary only to see these particles.