141. Giving Brothers Aliyos
23:13 We do not call two brothers for successive aliyos. This applies even if they only share the same father or the same mother. The same law applies to a man and his son or grandson. The reason for this is because of ayin hara (the "evil eye," i.e., a sense of jealousy) we do not do so even if the people in question say they are unconcerned. This law is even the case when one is called for the last aliyah and the other for maftir. If, however, maftir is being read from a second Torah, it would then be permissible. It is also permitted if the one being called for maftir is not yet bar mitzvah. In all these cases, if one was called and went up, he should not descend. Brothers who only share the same mother, or a grandfather and his grandson, may accept successive aliyos if they are called even if they have not yet gone up. In a case of need, relatives may be called for successive aliyos. (The Mishnah Brurah treats a man and his grandson with the same degree of stringency as a man and his son, not a degree more lenient – MB 141:19.)
23:14 One who received an aliyah in one shul and later was called for an aliyah in another shul may accept the aliyah and say the blessings even if it's the same portion he received earlier.