John Stamos showed love to his “brother” Dave Coulier on Instagram Wednesday after Coulier, 65, announced that he’s been diagnosed with stage 3 cancer. Stamos, 61, posted a tribute with various photos of the pair over the years, as well as an emotional message to his longtime friend.

Stamos vowed to be "be by your side through it all." John Stamos is showing some brotherly love to his Full House costar Dave Coulier. After Coulier revealed today that he's been diagnosed with a "very aggressive" form of cancer,

As an additional tidbit for Full House fans that isn’t quite so downbeat: Dave Coulier revealed in the latest episode of Full House Rewind that he now has a new co-host in the form of fellow sitcom vet Marla Sokoloff, who famously portrayed Gia Mahan on both the mothership series and its follow-up.