I want to check lineage specific duplications , to this end I am going to use ensembl orthology data which tags orthologues genes with homology type 'onetomany' in species in which one of them has several paralogues of the gene (undergone duplication) while the other species has only one copy of the gene. I have two concerns here , 1) is this a appropriate appropriate to identify lineage specific duplication, 2) in ensembl, how could you tell in a 'onetomany' relationship which species has only one paralogues and which one has several?

I appreciate any hints.