Alexandre de Lorraine was born to Philippe de Lorraine and a certain Claude de Souches or possibly Mademoiselle de Fiennes, both are mentioned as his mother. His year of birth was between 1668 and 1674, 1670 being the most common year mentioned.
Alexandre was one of several children fathered by the Chevalier de Lorraine, the infamous paramour of Louis XIV’s brother, which according to Madame de Sévigné were raised as her own by Catherine de Neufville, the wife of the Chevalier’s brother. Catherine de Neufville and Louis de Lorraine had fourteen children themselves.
In 1674, Alexandre was formally acknowledged and legitimised by his father, which allowed him to inherit property. He thus became the Chevalier de Beauvernois, named after a small seigneurie in Burgundy and was able to carry the last name of his father. (He seemed to have preferred not to do so and went by Alexandre de Beauvernois most of the time, perhaps to ‘avoid’ the bâtard for bastard in front of Lorraine.)
The Chevalier de Beauvernois went for a military career, perhaps encouraged to do so by his father, who was a great swordsman himself, and did not do too badly. In 1690 however, the circumstances are not quite clear, Alexandre defected the French Army and headed to Germany afterwards.
There he married into two of the most influential families of the Hanoverian court. His chosen bride was Eva Antoinette von Uffeln, who happened to be closely connected to the family of the favourite lady-in-waiting of Liselotte von der Pfalz. One could say the Chevalier de Beauvernois married the enemy of his father, who was not too fond of Liselotte or her ladies. The marriage took place in 1695 and their first child, Friederike Wilhelmine de Lorraine de Beauvernois, was born in 1702. The year the Chevalier de Lorraine died. Another daughter, Sophie Friederike de Lorraine de Beauvernois, followed in 1708.
Alexandre returned to the military again, but not the French, he fought for the Holy Roman Emperor and afterwards for Sweden in the Polish war. Then for Poland.
Alexandre seemed to have died either in 1724 or 1725. Through his children Alexandre is related to the Counts of Platen-Hallermund and Counts of Oeynhausen, the latter line can be traced back until today.