I think how it's said in English is "My family has 4 people in it; my dad, my mom, my older brother, and me," and in Japanese, I know how to say that. What I don't know is how I'm supposed to connect the two sentences together. Do they have a specific phrase or particle for that, or do they just use :/; like in English?
This is the best I got: Ex. 家族は四人;父と母と兄と私です。
You can list multiple items using と, as you wrote in your post: 父と母と兄と私. But if there are more than 2 or 3 items, it is more preferable to use commas in place of all but the last と: 父、母、兄と私.
The idiomatic way to say that your family has four people in total: mom, dad, brother and you is
私は父、母、兄と私の四人家族です。
Note that you can also say
私は父、母と兄の四人家族です。
You would do it as you do in English. You have to first note that "a list of items" does not have a verb, and therefore is just an array of nouns, not a clause, therefore there is no need to go into grammars on how to combine main clauses or relative clauses.
To list a string of noun, you simply list them one by one. If there are not too many terms, you can use と to connect them, or if there are a lot, simply use commas(or short pauses if spoken), then only add と (or something like そして) before the last one.
My family has four people: my dad, my mom, my brother and me.
家族は四人います。母、父、兄と私です。
