It was revealed in volume 2 of RWBY by Yang, that Summer was Taiyang's second wife. After his first wife Raven abandoned him and Yang, Summer came to help him raise Yang. During this time, him and Summer fell in love and eventually got married and had Ruby together. A few years layer, Summer left to go on a mission and was never seen again, it was presumed that she was deceased. This left Taiyang heartbroken and "shut down" after having lost his second love.
It was then revealed by Qrow in volume 3 that him, Raven, Taiyang and Summer all used to be apart of team called team STRQ. During Team STRQ's prime, Summer and Tai were close friends. The two also had similar light-hearted, easygoing, silly personalities. In volume 3 chapter 1, Taiyang and Ruby are shown together visiting Summer's grave. Taiyang says nothing while at his wife's grave.
Tai is shown to be not over Summer's death as he rarely speaks of her. He then later on tells Ruby that her personality is very similar to Summer's. After her death, Tai then continued raising the girls on his own in her honor. Tai was also aware of silver eyed people and never told Ruby about it, for fear that the same fate that befell Summer would befall her as well. In the picture of Team STRQ, Taiyang and Summer are shown standing next to each other.
Yellow Rose is a semi-popular couple in the RWBY fandom since they were one of the few canon couples in RWBY. Even though they have yet to be seen on screen together, they were married and had a child together. Some infer that the two were best friends before they eventually fell in love. Some have suggested that during their time at Beacon, the two had a similar relationship to that of Ruby and Jaune. They have a small fanbase on tumblr. They are both still the only members of team STRQ whose weapons and semblances have still never been revealed yet.
- Their ship name comes from the fact that yellow is Taiyang's main theme color and Summer's surname is Rose.