The relative pronoun 'that' has two cases — nominative and objective — and has no possessive case.

Literal

Relative-pronoun [possessive-の] 'that' [topic-は], nominative-case objective-case [possessive-の] two [copula-であり], possessive-case [topic-は] not-exist.

More English grammar terminology in Japanese. 関係代名詞 'relative pronoun,' 主格 'nominative case,' 目的格 'objective case,' 所有格 'possessive case' — all standard Japanese linguistic terms. ~であり is the formal continuative copula.