The way to read these verses is to understand what "brother" and "sister" meant to the speaker, and it did not necessarily mean biological offspring as we today understand the words. This is because we see use of these words in the Bible that clearly is not about biological siblings, e.g. Lot and Abram, or the children of Mary of Cleophas.
On the other hand, that "this is my body" and "my flesh is food indeed" are insisted upon as literal meaning and the apostles understood them literally (1 Cor. 11)
UNMITIGATED NONSENSE YET AGAIN.