Are a father and son allowed to have Hagbahah and Gelilah on the same Sefer Torah.
In some circumstances it is permitted, but it is preferable to avoid the practice.
A father and a son should not be called up for consecutive aliyos to the Torah.
One reason for this is given by the Beis Yosef (Orach Chaim 146) as being because the reading of the Torah is like giving testimony (the Torah is called edus), and therefore pesulei edus can not called up for consecutive aliyos. Some question this rationale, for it is permitted to call up a minor, even though he is an invalid witness (see Gra).
However, the Mordechai (Sefer Torah 968) writes that although reading from the Torah is considered a testimony, it does not have the formal properties of giving testimony, and therefore in principle a father and son can be called up for consecutive aliyos. The reason, however, why people refrain from doing so, is because of ayin hara. This is ruled by the Shulchan Aruch (141:6).
Based on this rationale, the Mishnah Berurah (141:18, based on Eliyah Rabbah) writes that if father and son were actually called up, the second should not go back down from his aliyah.
Provided their names are not mentioned (and provided names are never used for calling up a person to maftir—Mishnah Berurah 141:21), the Shulchan Aruch (141:6) permits a father and son to be called up for shevi’i and for maftir, though some authorities maintain that this applies only to separate sifrei Torah.
Based on this leniency, there is room to permit calling up a father and son for hagbahah and gelilah, provided that their names are not mentioned, and not mentioned in general in calling up for hagbahah and gelilah (rather, the caller calls out yaamod ha-magbiah veha-golel).
However, Shutt Mishnah Halachos (3:20) writes that a father and son should not be called up for hagahah and gelilah.
The same principles apply for two brothers.