No. I really don't understand why so many people try to go with 'trust' for 'believe', but they are different verbs.
Maybe it would help to think of the phrase: "You can believe someone you trust" to underline the difference in the meanings of the two verbs.
In another question involving helping "your grandfather" the correct answer left off the possessive pronoun. There were some comments about not being able to assume whose grandfather it was, but it was stressed that the assumption is made in Polish and that it sounded awkward and clumsy to put a possessive with common items, such as grandfather. Here, we have another relative, a brother. So why is it not good to use the possessive with grandfather, but good when speaking about a brother. I am very confused.
I assume that the sentence was something like "I am helping my grandfather". The grandfather one is most likely to help is one's own grandfather, therefore it is redundant to say that "I" am helping "my" grandfather.
Here, it's "She" who believes "your" brother. The brother 'belongs' to someone else than the subject of the sentence, so it has to be specified. "Ona wierzy bratu" would be assumed to mean "She believes her (own) brother".
That is not what I remember the sentence to be. I think it was more along the lines of: " It is good that you help your grandfather." I think it was a question in "Present 4". The correct Polish answer did not include the possessive before grandfather. Someone suggested in the discussion that the possessive was needed and offered a scenario involving a neighbor (whom I assumed to be a non-relative), but they were told it just sounded odd to ever put a possessive in front of certain words. Seemed very categorical at the time. In English, if I were speaking to a sibling or a cousin, I too would not say "your" grandfather, I might say "our" grandfather, but I'd most likely not use any possessive. But if the English sentence includes this possessive, then the two speakers are not (closely) related and then it is necessary. So, when the Polish answer did not include it, and the discussion said it was wrong/clumsy to included it, I took notice. So, when another answer came up, involving a brother, the use of a possessive seemed to contradict the previous discussion.
I wrote "something like" but I didn't mean that it was exactly like that ;) Your sentence has "you" and "your", right? So it's still the most logical option, the one in which we just assume that 'you' help your own grandfather, and not "his grandfather" or "my grandfather". As here you have "She" and "your", the sentence is quite different.
I also don't see any need to use the possessive with the neighbour. If I say "Idę do sąsiada", that means that I'm going to my own neighbour, and not Janet's neighbour.
I know what you mean but my hearing is bad and I''m not sure of some words as I hear them. This is the cause of most of my errors. Gluchy
You can, but you can't use it as a translation here ;) That's "Ona wierzy w twojego brata".
How does wierz- get a y ending in the third person singular? Which class is it?