cousin brother
He is my cousin brother.
Saying cousin brother is a redundancy.
blunder mistake
He has made a blunder mistake.
The phrase blunder mistake is a redundancy. Blunder has already the word mistake in its meaning, a stupid mistake, so we don't need to add extra word--mistake--with it.
new innovation
We need new innovation in technology.
new innovation is redundancy. Innovation itself means a new idea, device, or method.