Umm, valonquar means "little brother." That's not in dispute, is it? I don't mean to offend, but this argument is kind of ridiculous. Because the person talking used "the" instead of "your", then the stated definition of the word is completely wrong -- despite absolutely no other evidence for that -- and it really means something completely else? I feel like I am taking crazy pills here. If Maggy had meant "father," she would have used the word for father.
That all said, I think Jaime is likely the valoquar, but in the little brother sense.
If there's any linguistic curiousity to me is why say "little brother" and only that, in Valyrian?
I think the point about "the" vs "your" is that "your" could only mean Jaime or Tyrion while "the" could mean someone else's little brother. It is not changing the meaning of the word, but questioning who's little broer is being refered to.