Quechuan languages, especially those of the south, share a large amount of vocabulary with Aymara.
[1] Terrence Kaufman[2] finds the proposal reasonably convincing, but Willem Adelaar, a Quechua specialist, believes the similarities to be caused by borrowing during long-term contact.
[4] Moulian et al. (2015) posits the Puquina language of the Tiwanaku Empire as a possible source for some of the shared vocabulary between Quechua, Aymara and Mapuche.
[5] An automated computational analysis (ASJP 4) by Müller et al. (2013)[6] also groups Quechuan and Aymaran together.
However, since the analysis was automatically generated, the grouping could be either due to mutual lexical borrowing or genetic inheritance.