"I thought ten years of being a mom felt wild … yet here I am at my son's 13th birthday ... mom is the BEST," she concluded her message. "HAPPY 13 Angel, forever standing by to cheer you ...

The model mom ... of her son, whom she shares with ex Tom Brady, Bündchen wrote a heartfelt message to the teenager. "We have a new teenager in the house ! Happy birthday my sweet angel!