Petyr Baelish was briefly Lord Paramount of the Riverlands before the First Era, though was poisoned by his younger brother, Emmon Baelish, using Tears of Lys before he could consolidate his rule.
Petyr is often recounted as a genuine man and a good ruler by his sister, Alicent Baelish.
Emmon Baelish, brother
Alicent Baelish, sister
Marq Baelish, cousin
"Petyr wanted to see the family at its height. He wanted to increase the revenue of the Riverlands tenfold. He wanted to rebuild Harrenhal and he wanted the love of his bannermen, which I believe he very much succeeded in." - Alicent Baelish, on Petyr