So it seems to me. The "ava" is really redundant, but it occurs in real estate documents, at least in Latin America.

Here's a previous KudoZ question on "ava parte", by the way: http://esl.proz.com/kudoz/spanish_to_english/real_estate/263...

"a suit brought by the appellant to establish against the first respondent his title as absolute owner to a quarter of two-thirds (or an undivided one-sixth share) in certain lands."
http://www.indiankanoon.org/doc/1634694/

"Thus, upon Louis H. Whitney's death, the two Whitney children became the income beneficiaries and presumptive remaindermen of their father's undivided one-sixth share of the Cunningham Trust."
http://caselaw.findlaw.com/ny-court-of-appeals/1529597.html