Norte is Porto's son with Galicia; however, nobody is aware of the fact aside from Galicia and Braga.
Norte was conceived when Porto was reconquered for the first time in 868, when the county of Portucale was founded by Vimara Peres – the same man that reconquered Porto(cale). But Porto never met young Norte until later, because Galicia didn’t think it was that relevant, and also because Porto, being a strategic place to invade Christian Galician lands (namely the best gateway to get to Braga and Santiago de Compostela), was pretty much constantly being attacked and jumping between Moors and Christians, so she put him in Gumarães where Braga can keep an eye on him. They only met in 988 when Porto was definitely reconquered. [headcanon by Queijo]