Pied-piping with relative clauses is attested in the Schumann sources only. In the other sources relativized prepositional phrases do not occur.
A pronominal status is also suggested by the occurrence of disi in relativized possessive constructions such as Wan pikien disi Mama lange tatá lassi. 'A child whose mother and father are dead' (van Dyk c1765: 11).
Source: Schumann 1781: 177
Source: Schumann 1781: 78