My brother has some of my genes.

We share some of the same genes due to our common parentage.

Therefore, helping my brother get laid will help pass my genes forward, which is the meaning of life.

Actually, precisely the opposite. Every human has the model ("DNA") for every possible configuration of human within themselves. If even one person reproduces each generation eventually you will be born again. And they will and you will be, such is the material representation of the cycle of life. But what is you? A you is shaped into form by living, two people of similar genetic stock can be very different depending on actions and reactions through their life.

Therefore, it is prudent to shape a you that is not suited to living in a horrendous animal world where it's kill or be killed. Using right actions and reactions one can rise above the animal world and shape themselves into a you that will be born into a suitable higher world after death. It is your duty to help your brother see this, the last thing he, or you, would want to do is reproduce.