On Tuesday, David shared a snapshot of himself and his new fiancée on a boat off the coast of Italy, which he captioned, simply, "Yup," along with a music note emoji -- thus reiterating Katharine's earlier tweet, in which she confirmed the engagement news by posting a diamond ring emoji.
In the comments below the pic, David's daughter Erin -- who is one year older than her dad's new fiancée -- responded to the photo, "Mommmyyy" along with three red heart emojis.
The comedy writer is best known for co-creating the VH1 mockumentary Barely Famous along with her sister, actress Sara Foster. Not missing a chance to rib her dad, Sara, 37, also got in on the joke, commenting, "Out of the country. What did I miss?"
David's engagement to the former American Idol star comes after four previous marriages. Foster was previously married to B.J. Cook, Rebecca Dyer -- with whom he welcomed Erin, Sara and daughter Jordan -- Linda Thompson and Yolanda Hadid, whom he split with in December 2015. All together he has eight children from his previous relationships.