"ist" at the end??
I have seen many examples where a sentence has "ist" placed at the end. Now as I am still young in German I have come to hear "ist" as "is" but when added to the end of a sentence it kind of just changes the inflection in a weird way that I can explain. Her is a great example..
Sag mir, was mit uns beiden passiert
Which kindly translates too..
Tell me, what happens to both of us!
But when you add ist at the end of it...
Sag mir, was mit uns beiden passiert ist
It places it in a passed tense.. Like so.
Tell me, what happened to both of us!
Why does ist at the end do this to the phrase and when would you normally use it properly?
What you're looking at here is an instance of the present perfect in a subordinate clause.
The present perfect (or perfect past, or just Perfekt) is the past tense most commonly used in spoken German, and it is most often formed by using haben as a sort of auxiliary verb along with a past participle. Wir haben es gemacht, ich habe etwas geschrieben. We did/have done it, I wrote/have written something.
But, there are some situations in which sein is used for the auxiliary verb instead of haben. The general rule is that you use sein when the verb is intransitive (never takes a direct object) and changes either the condition or location of something, but there are also a few verbs, many of which you will notice are verbs of motion, that just always use sein, including werden, gehen, reisen, fahren, bleiben, and sein itself (not a complete list). Wir sind durch den Saal getanzt, die Blume ist erblüht, ich bin hier gewesen. We danced through the hall (change of location), the flower was blooming (change of condition), I was here (sein is an exception verb), although sein is one of the few verbs where using the OTHER past tense (the preterite, which is rarely spoken, despite being shorter, and mostly just used in writing) is common, so you'd be much more likely to hear someone say "Ich war hier".
Now take that, and apply it to a subordinate clause, which it looks like you already know a little something about since you used one in your first example. The subordinate clause always kicks the conjugated verb to the end. In your example, if we took the subordinate clause and made it its own, non-subordinate sentence, it would look something like this: Etwas passiert mit uns beiden. So, passiert is the conjugated verb, and it gets kicked to the end when it becomes part of a subordinate clause.
Adding sein to make it a past tense sentence, it would look like this: Etwas ist mit uns beiden passiert. (change of condition, presumably) See, the formation of past participles gets a little messy, and I"m sorry in advance for barraging you with this if you haven't quite gotten there yet. The base case is ge+(verb stem)+t (hat gemacht, verb stem is mach[en]), but there are all kinds of exceptions. Inseperable prefixes replace the ge- (hat besucht), separable prefixes go before it (ist aufgewacht), there are strong verbs that keep an -en ending and may change the stem around (hat geschrieben), mixed verbs where the stem changes but they otherwise keep the format (hat gebracht), AND in this case, verbs that end in -ieren simply don't take a ge- for some reason, I guess it just doesn't sound good, so the past participle of passieren is passiert, and it looks just like the third person singular present tense conjugation. SO, the 'ist' you add to the end of the sentence is actually just the conjugated verb from the above sentence getting kicked to the end of the subordinate clause, and the passiert isn't quite serving the same purpose as the passiert from the first sentence.