What is the ruling on the oaths you repeatedly made, threatening your brother to tell your father about his actions, but then you did not do so? And are these repetitions considered idle talk (laghw) or binding oaths?

A nullified oath is what is uttered unintentionally. However, the mentioned oaths are binding, and expiation is required when one breaks them. According to the Hanbalis, one expiation is sufficient due to their overlapping nature, though it is more cautious to offer expiation for each oath. If one is unable to ascertain the number of oaths, one should investigate and offer expiation for what one is certain of or what one predominantly believes will clear one's conscience.