Deuteronomy 18:15 says "from among thee" or "from the midst of thee", however we do not find this in the Septuagint or any reference to it in the book of Acts of the New Testament.

The equivalent word in Greek of the Hebrew word "mik·kir·be·cha" is not found in the Greek Septuagint or in the book of Acts. This is clearly an interpolation by the masorites.
One must note that Moses was talking to Israel as a whole, as one person or as one tribe (Israel) and was using the singular 'you' and not the plural 'you'. This singular you is also used in the Septuagint.
The singular "you" here is the tribe of Israel not the tribes of Israel.
The brother or brothers of Israel cannot be Israel itself but a brother tribe, the Arabs.