If you have named cultivars, chances are VERY good they are grafted onto seedling rootstocks. Using the suckers, in that case, would not give you the same tree. You would end up with only straight species plants.

P.S. I guess you could imply this from what I wrote, but if we are talking Corylus avellana (common hazel / hazelnut tree) grafting is usually the way it's done. BTW, layering would be another possibility.