So, how's about this.
In 1611, Archduke Matthias becomes emperor. He has been betrothed to the Princess Elizabeth of England since 1609's Treaty of London. The girl is sent off with much fanfare from London - although there is almost as much muttering about her marrying a papist - and arrives in the Austrian Low Countries a few days later. She is received at Ghent by her brother-in-law, Archduke Albrecht, and his Spanish wife, Isabel Clara Eugenia. At Ghent she converts to Catholicism.
After a month fêted in the Low Countries, Elizabeth sets off across south Germany to the imperial capital of Prague. Matthias is impressed by Elizabeth's looks, calling her his English rose. The unhappy pro-Catholic courtiers (who had been hoping Matthias would marry a Catholic) react by remarking that she's more a Scottish thistle. Elizabeth is not impressed with marrying a man who is older than her dad, but she IS conscious of royal duty. And within a year of the wedding, Elizabeth has given birth to a boy, Ferdinand Jakob (b.1612). The royal couple will not be "in love" but they are certainly well-matched. Their second daughter, Elisabeth follows in 1614, then boys, Friedrich Matthias and Karl Maximilian in 1614 and 1616. Another daughter, Maria Luise is born in 1618. Maria Luise's twin, Anna Katharina, will unfortunately die shortly after her father, the emperor.
Of course, when Emperor Matthias dies, followed by the death of her youngest daughter, Elizabeth goes mad with grief. Her mother in England is concerned for her daughter - who refuses to eat or change clothes. The whole succession is also open to question. Matt's eldest son is the obvious choice as king of Bohemia and Hungary, but what of the imperial title? No way can a child control the princes of the empire. Archduke Albrecht in the Netherlands is the natural successor, but the electors regard him as a "more Spanish than German". However, he has no children of his own, so he would make a good interim emperor (just until Ferdinand Jakob comes of age). The other candidate for the job is Ferdinand of Inner Austria. However, he and Elizabeth don't get along, plus, he hasn't liked his namesake godson since the boy's christening (probably more due to his Protestant mother than anything else). So while the electoral college dithers, Elizabeth has her son crowned as king of Bohemia in St. Vitus' Cathedral. The archbishop comes forward, places the crown on Ferdinand's head and then removes it to Elizabeth's, signifying that the royal power will be exercised by the Queen Regent until the young archduke turns 21.