If someone does not care about it, does Ayin Hara affect him?
Reb Moshe in the Iggras Moshe (אה''ע חלק ג' סימן כ''ו) says NO. Even though the Gemara (פסחים ק''י ע''ב) says the Heter by Zugos (eating or drinking paired items) nonetheless Reb Moshe says the same applies to Ayin Hara.
It would seem the Mishnah Berurah disagrees with Reb Moshe. In Hilchos Kriyas Hatorah (Orach Hachaim 141:6) it is brought that two brothers should not be called up one after the other, and he says that that's even if they are not Makpid. This seems to indicate he thinks Ayin Hara does affect those who do not care.
With regard to the ayin hara of two brothers or a father and son getting aliyos one after the other, the Aruch Hashulchan (O.C. 141:8) states:
ומאן דלא קפיד יכול לעשות כמו שירצה
One who is not particular about [ayin hara] can do as he wants.