I don't understand why do you think Portugal is younger than Spain. Spain is not considered Spain by historians until the union of the four kingdoms that conformed what is Spain today: the kingdoms of Castile, Aragon, Granada and Navarre. And they weren't united until 1516, under the rule of Carlos I. Portugal had been a kingdom for many centuries by then. Castile was not technically Spain, nor was Leon, that is inaccurate. They eventually became Spain, yes, but it's not the same.
We know that but Leão, Castella, Navarra and the others that later become Spain all existed BEFORE Portugal become an official Country.