Question

Would using Kyurem-B and Kyurem-W on the same team be considered species clause?

Answer 1

Yes, as Species Clause bans Pokemon with the same Pokedex number.

>Species Clause - A player cannot have two Pokemon with the same National Pokédex number on a team.
For example, using a team with two Koffing would break this clause.
Using different formes on the same team, such as Rotom-W and Rotom-C, also breaks the clause since they share the same Pokédex number (#479).

Source

Comments

actually you cant have both forms at the same time so...

Answer 2

Yes, they share a pokedex entry and are the same Pokemon.