Too much familiarity breeds contempt. What is sauce for the goose is sauce for the gander. Like father like son. A chip off the old block. The apple never falls far from the tree.
Blood is thicker than water.
Comparisons are odious. Company in distress makes trouble less. What a man has by nature lasts to his grave. You can't change a leopard's spots. Good breeding is the blossom of good sense.