Hey Spandan

There is no problem if your brother has decided to drop his BSc degree and go for engineering (it is never too late to choose your course).

There are many students who decide to do engineering or medical after completing their graduation from basic science questions (I have met people who have dropped 5 years straight for neet).

It is true that he might face difficult and non empathetic questions regarding why he left it but that is something he will have to prepare himself for but it will be worth it as long as engineering is his passion. Also, he can pick up skills that will make him the most eligible graduate for placement (besides trying t score above 8 sgp). All the best!