About the Birons of Courland
It´s interesting that the first von Bühren, Carl, son of a man named Mathias, went to Curland from his country, Westphalia, when a wesphalian man, Gotthard von Kettler, became the first duke of Courland. I suppose that a lot of westphalians, specially all the westphalians from the zone of Melrich, where the father and mother of Gotthard had their castle, were determined to improve their fortunes in the new dukedom of Courland-Semigalle.
Carl von Bühren, married with Odilia Krey, became a servant of duke Gotthard, and the duke granted him with a good portion of land in Kalnzeems. A grandson, also named Carl, was a groom in the service of duke Jakob, himself a grandson of duke Gotthard. So the von Bühren or Biren where well connected to the Kettler dinasty, but they were not more and not less that landowners. Carl, grandson of the Carl who served Jakob, who was grandson of the Carl who served Gotthard, married Hedwig Catherine von Rabb, a woman of similar origins. They had, I think, nine children. One of the children was Ernst Johann.
We know that Ernst Johann tried to conquer a place in the court of poor Charlotte, wife of tsarevich Alexis, but he did not succeeded in his plans. But, at this time, a russian princess, Anna Ivanovna, became duchess of Courland by her marriage with Friedrich Wilhelm Kettler. In the trip from San Petersburgo to Mitau, the husband of Anna was suddenly dead, and she went to Mitau as sovereign duchess. I suppose that Ernst Johann knew so well that the russian representative and advisor of Anna, Bestuzhev, was linked to one of the sisters of Biron...One sister of Ernst Johann, I don´t know who, was the mistress of Bestuzhev, so Ernst Johann had open doors in the little Courland´s court. Later, he managed so well and replaced Bestuzhev as favourite advisor of Anna Ivanovna...