There is no grammatical rule against attaching relative clauses to other relative clauses in English.
In a highly inflected language like classical Latin, it is possible to insert a seemingly indefinite number of clauses to others, as anyone who has been assigned to translate a page-long sentence of Cicero knows. But English is weakly inflected, and highly dependent on syntactic markers like word position and proximity to deliver meaning. The more dependent clauses you add to a sentence, the more awkward it sounds and the more difficult it becomes to parse, whether in spoken or written English, so there are practical limits to how many levels of recursion your reader will tolerate.
Marcel Proust is infamous for some long sentences, which have been the subject of competitions and even artwork.