Millie Bobby Brown and husband Jake Bongiovi welcomed a baby boy, sharing the news on Instagram on Thursday. In a sweet photo of the pair holding the infant’s hand, Brown wears an Isa Grutman diamond “mom” ring ($2,780) on her right middle finger. “hi little guy!” reads the caption of her post. The ring — which fellow boy mom Hailey Bieber also owns — features a band that splits into three, one holding each letter of the word, with a spray of diamonds totaling 0.25 carats. The couple hinted at their latest addition almost two weeks ago, sharing a video on Instagram of her growing family. The video, shot from the back, features Brown,…