Justin Bieber supports his siblings and the Rev It Up for SickKids fundraiser

Jazmyn, Jeremy, Jaxon, and Justin Bieber.Jeremy Bieber Twitter

Pop superstar Justin Bieber tweeted his support for his siblings this week in their effort to raise money for The Hospital for Sick Children.

Jaxon and Jazmyn "Jazzy" Bieber have joined the Rev It Up for SickKids campaign to raise funds for the Toronto pediatric center, and Justin encouraged his nearly 53 million Twitter followers to support them.

"Support my lil brother and sister #givingback @JaxonBieber @JazmynBieber," he wrote on Tuesday, including a link to his siblings' donation page.

Rev It Up for SickKids is an initiative founded in 2012 by a group of motorcycle enthusiasts in Ontario. In March 2013, the group pledged to raise $500,000 for The Hospital for Sick Children, also known as SickKids Hospital.

"These funds will be used to purchase NIRS equipment (Near Infrared Spectroscopy Technology), used to monitor oxygen levels, and to assess heart's ability to distribute oxygen throughout a child's body," Rev It Up explains on their website.

"The machines represent leading edge technology, and will go a long way to help the treatment of patients with heart ailments at SickKids."

One fundraising event to reach the half million dollar goal is their Rev It Up for SickKids bike rally.

On July 20, the group and their supporters will ride to a Greater Toronto area landmark to show support for the patients at SickKids Hospital. Donors can raise $1,000 to participate in the rally as a motorcycle rider or passenger, or to drive their exotic car. Raising $250 allows participants to ride the Rev It Up party bus.

Supporters who do not want to participate in the rally can still donate monies to the Rev It Up campaign, or sponsor another individual. Jaxon and Jazzy Bieber created a donation page, and are asking people to sponsor them. So far, the four- and five-year-olds have raised $755 of their $25,000 goal.

Their father, Jeremy, has also been faithfully promoting the Rev It Up for SickKids cause over the past week.

"Thank you again for all your donations to Sick kids hospital," he tweeted Wednesday. "There is no greater cause than our childrens future. #revitup #kidsforkids."

Rev It Up has raised over $25,000 towards their $100,000 campaign goal.