How long has the name Lose been used by your family? Who was the first person to use it and when did that person live?
Lose could also be a Tongan version of the English word ROSE- the flower, or ROSE - the surname.
Even if the name LOSE suddenly appeared in your family, it need not mean that there a Portuguese involved as a member of the family, it could just have been borrowed as a name because someone liked the sound of it, or knew someone of that name and called a child after that person.
Christine