reporter: their video received just a few views when first posted, but recently, when joseph s relative posted it to honor him on world down syndrome day, it went viral. now with more than 4.5 million views on tiktok and 24,000 on instagram. you want to sing our song. yeah. reporter: this time, joseph and papa dave singing to each other together. it s love. it s just unconditional love. reporter: an enduring connection across generations, rooted in the power of a song. what a wonderful world oh yeah oh, yeah, that smile. thank you so much for watching. i m linsey davis. for dav building a better bay area, moving forward, finding solutions. this is abc7news.
Finally tonight, the grandfather with a song for his grandson on his birthday, what a wonderful world and america strong. i see trees of green reporter: a priceless moment between a boy and his grandpa. that s joseph italiano and his papa dave singing to him what a wonderful world at joseph s birthday celebration two years ago. what a wonderful world it s just the words of the song, the connection that they have. skies of blue reporter: joseph was 5 at the time. he has down syndrome. his parents say his personality is magnetic. and his grandpa dave takes him everywhere. it just seemed like a perfect song for joseph. he s a treasure to our family. i ve been singing it to him since he s been an infant. i see friends shaking hands