Canonical Raith family tree guide reference:
Nine surviving sisters. Inari, Lara, Natalia and Elisa and attic sister are confirmed of them. This means four others exist but are not explicitly identified - Felicia Raith could be a sister or otherwise a cousin.
None of the explicitly named Raiths were amongst the other two at the front with Lara defending the line in White Night. Dresden meets the other named ones after then and while they may have been amongst the other three present in the background, too much attention was paid to those two for them to then not be recognised later.
Unknown deceased brothers and sisters Lara refers to (in a high stress/emotion situation) as countless in number.
Tania is definitely not a Raith sibling. She would have been only ten during Blood Rites when Lord Raith was deposed and then Inari was explicitly the youngest.
Madrigal Raith mentions his and Thomas’ bloodline as the oldest in House Raith in reference to why their killing each other would not be tolerated. This does indicate the presence of other, “younger” lines.