Is it right to date your junior sister's friend?

Nothing wrong with it as long as it doesn't break their friendship.
Question is are you matured enough to handle such relationship?

I dont cee anything wrong in dating Ur junior sisters friend but d thing dat matters is how U would B able to handle both knowing dat dey are girls and ussually hard to get along with if am U if D girl is very pretty and well behaved i would go 4 her but wen i get her i must try to maintain my respect by warnin her not combine my r/ship with her and andn dat ov my small sweetie cos girls can really gossip. wishin U D best

No and Yes. No, because she's younger than you are, and most Nigerian men like to date ladies not as old as they are (but she must be 18+). Yes, because she's your younger sister's friend. How would you handle your sister, when she discover her friend is dating her elder brother. How will she also feel, so think of that. You should know this before you go into it.

For me, I will tell my sister I'd like to date her friend, what she says will determine my next step.