“Happy birthday to the most precious angel on earth! you’re my favorite person that ever existed 🙂 i love you sm,” he captioned an Instagram pic of himself giving the singer a piggyback ride.
“One more for the queen,” he added in a second snap. “Words can’t express what a real fucking treasure this one is.”
Grande liked both photos and gushed: “I love you so much.”
Us Weekly exclusively confirmed earlier this month that the couple – who only began dating in May – are engaged. Davidson was most recently dating Cazzie David while Grande romanced Mac Miller.
The couple has been gushed over each other on social media since the news broke. So much so, that even Seth Rogen trolled the pair.
“Guys seriously,” he commented on one post last week. The Saturday Night Live star, 24, replied: “@sethrogen when ur getting married to the hottest girl in the world you tell me how you’d act.”
Although Davidson and Grande are very serious, a source told Us that they plan to have a long engagement.
Sign up now for the Us Weekly newsletter to get breaking celebrity news, hot pics and more delivered straight to your inbox!