Reese Witherspoon<\/a> is no stranger to sharing glimpses of her life on social media, whether it\u2019s hopping on the latest trend<\/a>, teasing a new project<\/a> or posting sweet moments with friends<\/a> and family<\/a>. But her newpost will have you doing a double take, thanks to a rare appearance from someone we don\u2019t often see: her youngest son<\/a>, Tennessee.<\/p>\n The Morning Show<\/a> actress, 49, took to Instagram to mark a major milestone\u2014Tennessee\u2019s 13th birthday. She shared a heartwarming photo of the two standing by a waterfront railing, with the rippling blue water in the background. It\u2019s a lovely moment, but what really caught my attention? Just how much Tennessee looks like his dad, Reese\u2019s ex-husband Jim Toth.<\/p>\n From the hairline to the eyes, it’s easy to point out the uncanny resemblance. They\u2019re basically twins.<\/p>\n \u201cHow is it possible that my youngest boy is 13?!\u201d Reese wrote in the caption. \u201cHe never ceases to amaze me with his joyfulness, his brilliant sense of humor and his endless curiosity. I love you so much, Tenn!\u201d<\/p>\n Kevin Mazur\/VF20\/WireImage<\/p>\n The comments section lit up with birthday wishes for Tennessee, including one from author Harlan Coben who chimed in, \u201cThe youngest keeps us young. What a gift. Happy Birthday!\u201d<\/p>\n Of course, resemblance runs strong in the Witherspoon family.<\/p>\n Just earlier this month, Reese posted a similar birthday tribute<\/a> to her daughter Ava, who turned 26 and the two look identical. In the photo, the duo pose with arms wrapped around each other, both flashing bright smiles. Aside from their slightly different hair colors (Reese\u2019s signature blonde vs. Ava\u2019s deeper brunette), their blue eyes and facial features are nearly indistinguishable.<\/p>\n Looks like strong genes\u2014and sweet birthday tributes\u2014are a Witherspoon family tradition.<\/p>\n Want all the latest entertainment news sent right to your inbox? Click\u00a0here<\/a>.<\/p>\n<\/span><\/div>\n