It seems to me that the House of Habsburg went over into the House of Habsburg-Lorraine in the 18th century. But where does that leave the descendants of the original House of Habsburg? (originaly it was thought there were none left)
There are a few impoverished royal descendants around, I believe in Hungary, Austria, Switzerland, Netherlands, and Spain. Are they answerable to the House of Habsburg-Lorraine or are they regarded as an independent house? And how are, or should they, be recognized by other royal houses and countries.
Empress Maria Theresa, her sister Archduchess Maria Anna and their first cousins Electress Maria Josepha of Saxony and were the
last dynasts of the Habsburgs. When MT married Franz Stephan of Lorraine, they had permission to rename their house/descendants into Habsburg-Lorraine (from the Pope, if I'm not mistaken). MT carried on the Habsburg line as her sister Maria Anna (who married the younger brother of Franz Stephan) and her only child both died during and/or soon after childbirth. Their 2 cousins married into other houses and were not allowed to carry on Habsburg line, although they (and their husbands) both fought for the crown lands of Austria.
I'm not sure whom you're referring to as the other line(s)/impoverished royal descendants of this house. The only line that is ever recognized from the 18th century onwards are those descended from MT in the male line and formed different branches: the main branch, Austria-Tuscany, Austria-Este, Austria-Hungary, and Austria-Teschen.
If the Head of House then (Philip II of Spanish Habsburgs) did not give his consent to the marriage of his half brother Juan, then Juan's descendants have an even weaker claims on anything (other than those given to him by his father or half- brother). Indeed, The Spanish succession at that time recognize females as successors to the throne, there was no need to recognize him or his descendants as dynasts (even though Juan's father recognized him as a son). I'm not sure if this existed at that particular time but the Austrian line could succeed the Spanish line and vice versa.
On any claims on the Habsburg-derived wealth, I believe there is not much to be claimed, if any, from the Spanish Bourbons (main line in Spain today), who do not own very considerable (private) properties now. The cadet branches (Two Sicilies & Parma) of the Spanish Bourbons seem better off as far as I know.....According to royal historian Arturo Beeche, Duke Robert I of Parma remained very wealthy despite being deprived of his duchy: "
Not only did he receive a considerable amount of lands and palaces from his Parmesan inheritance, but he also received a fantastic endowment (both financial and territorial) from his uncle the Comte de Chambord, which included large properties in France and the Austrian empire.The confiscation of the Chambord estate was a huge mess. Eventually the French government had to compensate the Bourbon-Parma family".
So, Bourbon-Parma is wealthy on their own even after losing their duchy because of their inheritance from their Farnese and Bourbon/Chombard lines, not because of Spain although they received titles and appanages from it. Note that Duke Ferdinand I of Parma (also Infante of Spain) pleaded with his son Louis (during the exchange of Parma/Tuscany/Louisiana in 1801) to remember that
Parma (from Louis' Farnese great-grandmother) was the family's only real assets. Similarly, the Bourbon-Two Sicilies branch of the Spanish Bourbons was also considerably endowed from their Farnese inheritance.
As for the surviving Austrian line of the Habsburgs, I read sometime back that they are trying to get properties and money from the Republic of Austria, those that
originated from the fantastic trust fund left by Franz Stephan (from his own private fortune as he was a very talented businessman) for family members who may need it. I also read that they were able to get back some properties in a few of their other heredity lands under the Austrian crown.
So, using all these facts on the private wealth of the existing Spanish Bourbons and the Austrian Habsburgs, what can the Juan's descendants claim from these houses now?
I do know of an expert on the Spanish and Austrian Habsburgs (especially 16th-18th centuries) and their various succession laws although he belongs to another royalty forum. I could ask him if you can send him a message or what. Just send me a PM about it. He can answer your queries much better!