But in English, "sibling" is gender neutral. Can you only say "Raj and Peter are brothers" in Hindi? Or if you can say "Raj and Peter are siblings", would that still use "भाई-बहन" even though both are male?
It is surprising that in a language that has so many specific names to describe relationships within the family, that there is no name to define fraternal bonds !
Same thought for parents = father - mother
Grandparents = grandfather- grandmother.
When u say that they are brothers, u may say either वे दोनों भाई-भाई हैं or वे दोनों भाई हैं though the second alternative is generally preferred. The same is the case with sisters, though the use of बहनें is preferred.