Taliyah and Sivir looks like they belong to different races

Shurima is a desert the size of a country. It can have multiple ethnic groups.

: Hello, grandpa. : You're adopted.

well sivir technically is royal blood, and families with high social status are usually picky with marriages that are partially based on looks alongside status and wealth among other things... so yeah it's very possible the difference could be Sivir is heavily influenced by genes from possibly many generations of selective marriages that have an impact on her looks whereas Taliyah AFAIK is a possible regular Shurima common citizen with regular commoner parents and she just happens to have affinity for earthen based magic

Sivir has royal blood... and she has a lot of money! while Taliyah has been traveling through the world since early age so she has no clue what tweezers are or anything, she's also not worried about how she looks but what she can and cannot do with her powers.

They both look like from the same race to me, human race.

I mean I think so, ex. There are brown pinoys and white pinoys but they are still both pinoy. White pinoys were either mixed from spanish spain or never went outside. is shuriman still but maybe the ingame model and splash art are different. She should be brown like Taliyah if she isn't already.

You are aware that Sivir will be getting new splash arts to replace all those that were changed with the "unification". When I look at Victorious Sivir, I noticed a facial struture that was not nearly as slender as her default splash.

When the design team gets to Sivir's artwork, I anticipate a slight change in her appearance to mark her differently than the other cultures of Runeterra.

They look pretty similar. If you put them beside each other, they have similar skin tones and such. Note that Taliyah is a lot younger.

Different tribes I suppose. I do miss Sivir being Noxian though :P