EN
We show that a comeager Π₁¹ hereditary family of compact sets must have a dense $G_δ$ subfamily which is also hereditary. Using this, we prove an "abstract" result which implies the existence of independent ℳ ₀-sets, the meagerness of 𝒰₀-sets with the property of Baire, and generalizations of some classical results of Mycielski. Finally, we also give some natural examples of true $F_{σδ}$ sets.