Yancy died of a heart attack on Monday.
Timolin and Casey Cole are still upset over Natalie Cole's GRAMMY tribute.
They say the 'good intentions... did not come through.'
The 'Unforgettable' singer did not receive a solo tribute, but was included in the telecast's 'In Memoriam' segment.
Celebrities and fans also voiced their disappointment that the singer wasn't honored with a special tribute.
The moving 'celebration of life' featured the singer's favorite people and songs.
Cole died at the age of 65 on New Year's Eve
The 65-year-old singer, who died on New Year's Eve, suffered from a 'serious and progressive disorder' that led to heart failure.
Following Natalie Cole's death, ET sat down with her sisters Timolin and Casey, who revealed why their sister suffered in secret.
Following the singer's death, ET sat down with her sisters Timolin and Casey, who revealed why their sister suffered in secret.
Robinson revealed what he would miss the most about his longtime friend.
The singer of "Unforgettable" and "This Will Be", among other iconic songs, has died.
ET remembers the celebrities who died this year.
