Constance, who just recently married partner Denim Cooke, is now step-mum to his two teenage sons, Zeyke and Sunny.
"Marrying somebody with children is marrying them all as a team," she said.
"It's not committing to parent their children. It's committing to working towards each persons individual needs as a team a team that we call family."
The best-selling author and her new partner welcomed a child together in May, a baby boy named Raja Wolf.
She also has four children from her previous marriage - Rumi, Snow, Arlo and Billie-Violet.
Despite claiming step parenting was "tricky", the "rewards are exceptional".
"No, I’m not their mother," she wrote.
"That’s a title that belongs to a woman who may not be alive anymore but certainly deserves to take the credit along with their dad for these incredible boys."
"But one day they will marry, or have a baby, or land that job or win some world championship skate comp and just like a mother I will be there, sobbing my eyes out with pride."
"I love these two boys and all I except from them in return is to never forget that," she added.
Constance's post has been liked over 10,000 times and has been inundated with comments of support from fans.