I would like to know why the writer said "You have to understand, my own son is practically grown up."

As I told you, I’ll be gone until Wednesday morning. Thank you so much for taking on my “children”while
I’m away. Like real children, they can be kind of irritating sometimes, but I’m going to enjoy myself so much
more knowing they’re getting some kind human attention. Remember that Regina (the “queen” in Latin, and
she acts like one) is teething. If you don’t watch her, she’ll chew anything, including her sister, the cat. There
are plenty of chew toys around the house.Whenever she starts gnawing on anything illegal, just divert her with
one of those. She generally settles right down to a good hour-long chew. Then you’ll see her wandering around
whimpering with the remains of the toy in her mouth. She gets really frustrated because what she wants is to
bury the thing. She’ll try to dig a hole between the cushions of the couch. Finding that unsatisfactory, she’ll wander
some more, discontent, until you solve her problem for her. I usually show her the laundry basket, moving
a few clothes so she can bury her toy beneath them. I do sound like a parent, don’t I? You have to
understand, my own son is practically grown up.
Thanks for supplying enough context to figure this one out! The writer is saying that her own son is nearly an adult. Apparently she misses having young children, so she has started thinking of her dog and cat as her "children."
The writer is usually "practically" to mean "almost" in this case (see the expression "for all practical purposes").