Ashlee Simpson celebrates her eldest son Bronx's special day with a sweet note

The 40-year-old singer took to her official Instagram account on Wednesday to mark Bronx's 16th birthday.

The mom of three shared a recent photo featuring the teenager, posing along with Simpson while holding a bouquet of roses.

"Being your mom has been the greatest joy of my life. You are my rock my soul. My ride or die. You have been the greatest blessing in life that I could have ever dreamed of," Simpson penned down in the caption.

The Pieces of Me singer also posted some throwback images of the Bronx as well as a snap of the birthday boy with his younger siblings.

The proud mom went on to say, "I would not be me without you. Thank you for choosing me to be a mom, and YOUR mom. You are so calm, consistent, brilliant, loving, kind hearted, thoughtful, funny, mysterious, and incredibly awesome. I thank God every day that I get to be your mom."

"You are a true gift to this universe and I’m so lucky you are my very grown, and cool baby… happy 16th birthday. I love you. Also you were born to this song. Thank you for making me the luckiest," Simpson concluded.

It is pertinent to mention that Ashlee Simpson welcomed the Bronx with ex Pete Wentz. She also shares daughter Jagger, 9, and son Ziggy, 3, with her husband Evan Ross.