Louis I the Great was King of Hungary and Croatia from 1342 and King of Poland from 1370 and he ruled both kingdoms until his death in September 10, 1382. His wife Elizabeth of Bosnia.
They had two daughters. Mary, also known as Maria of Anjou and Jadwiga also known as Hedwig.
Mary reigned as Queen of Hungary and Croatia between 1382 and 1385, and from 1386 until her death on May 17, 1395
Her sister, Jadwiga second daughter of Louis the Great was the first female monarch of the Kingdom of Poland, reigning from October 16, 1384 until her death in July of 1399.
Like second sons with respect to their older brothers, they often play second fiddle to their older sisters. It happens in both the world of royalty (e.g. Princess Margaret of the UK, known as the "rebel without a crown", younger sister of the queen -- a designation she resented, preferring to be known as the younger daughter of a king) and commoners (e.g. Princess Lee Radziwill, forever in the shadow of her legendary older sister, Jacqueline Bouvier Kennedy Onassis).
That being said, as with second sons who unexpectedly came to thrones (through death, succession wars, usurpations, changes of law, treaties, the branching out of dynasties), there have been a surprising number of second daughters who unexpectedly succeeded.
Good examples coming to mind are Queens Juana la Loca of Castile, Elizabeth I Tudor of England, and Mary II Stuart of Great Britain; Empresses Anna Ivanovna and Elisaveta Petrovna of Russia (interestingly enough, in each case the heir to the throne was a nephew through her older sister); and the Grand Duchess Charlotte of Luxembourg.
Are there other examples? What about the earlier history of Spain, and possibly Portugal? Or the ancient world (granted that this is harder to document)? Or outside Europe?
Of course, when it comes to queens CONSORT, one most certainly need not be the first daughter in a family ...