Are the brothers and sisters of a person whose father breastfed him for a full month without knowing the number of feedings considered brothers and sisters of my father through breastfeeding?

Your father became a brother to the man through fosterage if he suckled five or more times from his mother, and this is the most preponderant opinion. Or even if he suckled only once, it still establishes prohibition. The proof for prohibition is the saying of the Prophet (peace be upon him): "Fosterage prohibits what lineage prohibits." So, if your father suckled from the mother of the aforementioned person, he is a brother to him and to all her sons and daughters.