Lanee and Shapreea White wanted to set up a memorial for Standley next to the spot on Tam O'Shanter Drive where she lost her life. Their brother and Standley have a 5-year-old son together.
"We just grew a special bond with her and she became more of a sister to us than just our nephew's mom," Lanee White told FOX40.
Standley was riding her bike with a friend in the early morning when Stockton Police believe she veered into the road and was hit by a car.
Officers say drugs and alcohol were not factors in the crash. The driver was not speeding and stopped as well as cooperated with police.
"I'm still trying to figure out exactly what happened," said Gary Standley, Serena Standley grandfather.
The 23-year-old spent most of her life in Stockton and graduated from Venture Academy.
Her grandfather said she had cerebral palsy and while she wasn't able to use her right hand, she never let that hold her back.
"She was amazing to see the things she had done. She learned to tie her shoes one-handed," he told FOX40. "She did painting and artwork."
"She was that fun person and always made us laugh. And knowing that she's gone, it's hard," Lanee White said.
Serena Standley's death is the fifth fatal accident involving pedestrians, cyclists and cars in Stockton in the past three weeks. Her family hopes her story encourages drivers to be more alert.
"They need to pay attention. Need to pay attention to the road," Lanee White said.
"Slow down, OK?" Gary Standley said. "I mean that's the main thing. People are just too much in a hurry."