A month ago, my brother, a 64-year-old divorced man, did his Aliya in Israel. Will he be entitled to an old-age pension at retirement age?

Under the law, your brother is not covered by old-age insurance because he immigrated to Israel at an age above the legal age limit.
When he reaches retirement age, he may be entitled to a "special old-age pension", provided that he meets the requirements of the income test.
If, after a year passed since his Aliya, he has no income, he may submit a claim for income support benefit.