Zac Efron made a touching birthday tribute to his baby sister Olivia

Zac Efron is the sweetest older brother in the world!

In honor of his half-sister Olivia's third birthday Dec. 25, the High School Musical alum shared the cutest snaps of him cradling the toddler in his lap. He captioned the shots, which included one of him giving her a sweet kiss on the head, "Happy bday lil sis."

Needless to say, the rare pictures had fans soaring, flying to the comments. "Can you pls be the father of my children," one wrote while another added, "My ovaries oh dear god."

But bopping to the top was Zac's brother Dylan Efron, who wrote, "I think we spoiled her."

Indeed, Dylan has been prepping for this day for nearly a month. "My sister turns 3 on xmas day," he captioned a series of pics of him and Olivia back in November, "any gift ideas would be greatly appreciated! Just tryin to stay her favorite brother over here."