Having a hard time w/ High Valyrian Family lessons.
I'm finding that the higher up the High Valyrian tree I get, the more words there are that mean the same thing.
Example: There are a lot of words in different forms for "my" and other indicators of possession.
In the Family lessons, there are so many different words for "cousin." When in doubt, I just use "cousin," and that's usually correct. However, I don't feel like I'm really learning the words since I'm guessing so much.
There are also different forms of the same word that mean different things.
Example: "Qybra" is "uncle," but "qybranna" is "cousin."
Is this because familial relationships in this world are so complicated?
I think this might be dependent on the way that you look at things. For instance, most European languages have different versions of articles depending on whether the word is masculine or feminine (el/la and los/las for Spanish, for instance). Some languages even have more than two genders (often masculine/feminine/neuter). High Valyrian just happens to have four different "genders" (or "classes") - which is why there are so many forms of the word "my," for instance, because there are different forms for different classes. There is really no difference between having to learn which articles agree with which words based on the gender of the word in Spanish and learning which possessives agree with which classes in High Valyrian.
Familial relationships in HV are definitely very difficult, especially since we don't necessarily make same the linguistic distinctions in English. The only advice I can give you about that is to keep practicing. It was very difficult for me as well, in the beginning, and I was definitely guessing more often than not or just using the first word for "uncle" that I remembered if the English sentence only said "uncle."
As to words like qȳbor (uncle) and qȳbranna (cousin), I think it would be helpful not to think of them as "different forms of the same word." They're different words that have the same word root, which I think is actually very helpful because it means it can help you remember how words relate to each other. Think about word roots in English - for instance, if you know the word root "cardio" means "heart," then you can guess that words that include that word root have something to do with the heart (cardiovascular, cardiology, etc.) even before you know the meaning of the word. It's the same thing here. Qȳbranna and iāpanna both mean "cousin," but your qȳbranna would be the child of your qȳbor (mother's younger brother) and your iāpanna would be the child of your iāpa (mother's older brother). It's not because familial relationships in the ASOIAF/GOT universe are any more complicated than they are in the real world - it's just that the language makes linguistic distinctions using a single word between older/younger siblings that we don't make in English, for instance.
It takes a lot of practice, certainly, to try to remember similar words, and it's especially difficult in High Valyrian because, unlike real world languages, there aren't really opportunities to familiarize yourself with the words in a real-world context. Like any other language, the key to remembering is repetition and practice, which might be a little harder in High Valyrian, but it's definitely not impossible!
There are plenty of languages in this world that make similar distinctions when it comes to family relationships, which is why in linguistics, there's actually a way to classify languages according to which family relationship terms they used. High Valyrian uses an Iroquois kinship system. English, on the other hand, uses the Eskimo kinship system. Which is why we have far fewer terms for uncles, aunts, siblings and cousins. You just have to get used to it. If it keeps confusing you, I'd suggest making a relationship chart with the many terms.
As for the different forms for "my" - High Valyrian is an inflected language, those are really common in those. In inflected languages, the word order often isn't as rigid as in English, so they use declension to make it clear which word has which function in a sentence, and which adjective or possessive pronoun belongs to which noun. In High Valyrian, the adjective can stand before or after the noun it modifies, and that could lead to confusion if it wasn't for declension. For example:
"Muña ñuha kepe jorrāelza." - My mother loves the father. "Muña ñuhe kepe jorrāelza." - The mother loves my father.
If it wasn't for the declension, you wouldn't know which noun the possessive pronoun belongs to. It's hard to get used to if you don't already speak a language that has a similar system, but there is a reason for all those confusing forms.