Adopted daughter and raised by a young Bosmer named Cael, who is the adopted daughter of my Khajiit Nash-Keebah. Looong story and so very confusingly awesome. XD
There is little developed about Ma'Tri, other than she grew up with a large family of other orphans raised by Cael, was very fond of Sindri from day one, and went to he bard's college to become a dancer when she was a teen. Looks like she succeeded! XD