Amanda Seyfried is a doting mother to two young children, three-year old Nina and five-month old Thomas, but there's also another adorable member of their family.MORE: Amanda Seyfried's daughter featured in rare photoAnd on Instagram, the Mamma Mia! star shared the sweetest photo of the family's Australian-Border Collie mix, Finn, looking lovingly into the camera.The star didn't caption her Instagram post, and fans were immediately captivated by just how adorable the pooch was.WATCH: Amanda