I think my cousin is selfish for trying for a baby
Why do you think your cousin is selfish for trying to have a baby?
He gets a baby a while I get nothing.
If your cousin is trying to have a baby then as a family you need to be more supportive to him instead of being selfish. Family relationship is not a competition and if you treat them like it is, you will start giving yourself negative mental pressure and that is not good for your soul.
Haha I got you? No one should help others because it's not my problem.
You're family so any struggles they have is also your problem. Even if you want your own child you can still be there for your cousin and you may even enjoy spending time with your new niece or nephew. I know your cousin would appreciate the help.