Lucille (Lucy) Tracy is the wife of Jeff Tracy and mother of the five Tracy brothers Scott, John, Virgil, Gordon and Alan.
The official cause of her death is unknown but various different ways have been suggested, e.g illness, road accident and the most official death so far, avalanche (Thunderbirds 2004 and The Complete Thunderbirds Story)
Each Tracy boy is said to take after their mother in one way or another:
Scott- her determination
John- her love for the stars
Virgil- took after her through looks and artistic elements
Gordon- her humor
Alan- over all