Translation:He is my uncle, because my father is his brother.
In Serbian, we have 3 different words for English word "uncle":
stric/čiča --> father's brother; ujak --> mother's brother; tetak/tečo --> husband of my aunt (father's or mother's sister). :)
"This is my uncle" would be "ésto/éste es mi tío". http://www.spanishdict.com/topics/show/80 http://spanish.about.com/od/pronouns/a/demonstrative_pronouns.htm
Because "as" is "como" and "porque" "is "because". http://www.spanishdict.com/translate/como
You probably think it's the same, but logical words aren't interchangeable, even when they are close in the meaning. Here the meaning is the same, but we have to keep them, the meaning can easily change when we change them because they are very meaningful words.
A subject pronoun (in this case "he") is usually required in English with most verbs, it can be implied in Spanish, but you usually have to state it in English. "is my uncle" just sounds incomplete, "he is my uncle" makes more sense. You could technically say "it is my uncle" as well depending on the context.
Let's say someone asked you what you were thinking about, and you said: "It's my uncle, because my father is his brother."
As in what you were thinking about was your uncle, and you were thinking about him because he's the brother of your father. How would you translate this in Spanish?
In this case that's fine, the two are interchangeable in this sentence.
"Since" and "because" can be synonyms of each other and so "porque" can be translated as "since" (http://www.wordreference.com/es/translation.asp?tranword=Since), but it's more common to translate it as "because".
I said "He is my uncle because he is my father"s brother." Apparently I got it wrong. Duolingo is great, but it never excepts sentences that have the EXACT same meaning. I personally think that's a little dumb, cause I still understood the meaning of the sentence, I just typed it up a little differently. BLEH
"Es" can mean "he is, she is, it is," or even "you are." Spanish often omits the subject pronoun when the subject has already been established. For this sentence, "she is" and "it is" do not make sense. So we are left with the possible translations of "he is" or "you are," both of which Duo should accept, although I don't know if they do.