Justin Bieber has once again made a wish come true for a child battling cancer. 


The 17-year-old spent Valentine's Day with 6-year-old Avalanna Routh, who is fighting an extremely rare form of brain cancer. The two played board games, signed autographs for each other, and Avalanna was even "able to lay her hands on the famous Bieber hairdo and style it her own way."


A few days later, on Feb. 18, Justin once again took time to wish a 9-year-old cancer patient a happy birthday. Earlier this year, Trinity Petit was diagnosed with an inoperable form of brain cancer. With help from family, friends, strangers, and even a local news station, requests went out online to the famous pop star, asking him to send her a quick message.


You can see the shout-out below (which also features a brief cameo by Bieber's girlfriend, Selena Gomez). The pop star also recently announced that he will be writing a second book with publisher Harper Collins titled "Justin Bieber: Just Getting Started."


"Being able to share my story with my fans through these books is an absolute privilege," he said in a statement. "I can't wait to show them more about my life on tour and in the studio in this next book."


Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.

Justin Bieber sends birthday greeting to young cancer patient
9-year-old Trinity Petit is battling an aggressive form of inoperable brain cancer.