Here’s a pretty cool article about why we might be smelly, but can remain somewhat oblivious to it.

Essentially, the nerve endings for smell up high in your nostrils (olfactory nerves, cranial nerve I) become bored with the way you smell and are looking instead, for new input, fresher scents perhaps.

So it’s important to help a brother/sister out, letting them know if their smell is offensive.

http://www.businessinsider.com/human-beings-smell-blind-why-2017-5