At bedtime one night, my younger son Lucien, 31/2 years old, announced cheerfully: "I'm a girl."

"You're a boy," I pointed out helpfully.

"No! I'm a girl! You're a boy!" he insisted, bulldozing over my explanations about male and female anatomy.

"If I'm a good girl, can you get me a rabbit?" he inched closer to ask, ever so sweetly.

"Erm," I said, stalling for time, before giving up. "Okay."

In the seconds that ticked by, I mulled over this gender-bender.

Since he started speaking, at around 21/2 years of age, Lucien has been identifying himself as a girl on occasion.

I've never found it worrying, because kids as young as that have no idea what gender is.

In fact, I found it refreshing that he was completely unfazed by things his seven-year-old brother would freak out at: Using pink towels; buying Lego sets pitched at girls; and trying on my costume jewellery.

Make no mistake, though, Lucien is very much a boys' boy. He is crazy about cars and ninjas, and likes to enact a good swordfight as much as any bloke his age.

Once, when we took him to a seafood restaurant, he took a shine to a pretty waitress and kept asking us, "Where's the girl? Where's the girl?", while craning his head to look for her. When she smiles at him, though, he feigned nonchalance and hid his face.

At school, as far as I know, he has no problems with which category he falls into. When I take him to the toilet before class, he automatically heads for the blue-painted cubicles for boys, where he washes and dries his hands at the picture-coded station, proudly announcing: "This one is for boys!"

So, it disturbed me greatly when I stumbled upon an old, 2010 article on the Internet, from Britain's The Mirror newspaper, about a three-year-old boy who was diagnosed with Gender Identity Disorder and receiving psychiatric treatment for thinking he was a girl.

"He was referred to the Gender Identity Development Service at London's Portman and Tavistock NHS Trust last year after he told his mum and dad he prefers girls' clothes and playing dolls," went the report.

Really? That's a sin?

A quick Google search revealed some parents' concerns about their sons identifying with being a girl. One netizen, "Patrick K.

Freeman", in a two-month-old forum post, said he was a little worried that his four-year-old keeps telling him and his wife that he is a beautiful princess.

The "expert" who replied suggested that he take his child to a psychiatrist. Others chimed in with less-hysterical advice, I felt, to reserve judgment on his young son, and wait and see.

Then, there is the seven-year-old boy in Colorado, reported by The Los Angeles Times in 2011, who wanted to join the Girl Scouts and was turned down by the troop leader.

The Girl Scouts of Colorado then said they would welcome him only if he had said he was a girl, and his family was going to "entirely have her live her life as a girl".

To me, such pigeon-holing of children into socially acceptable sexual binaries is the same as bigotry. Why do children, still discovering who they are, have to decide so young which side of the fence they are and stick to it?

True, the bits that you are born with are, by and large, things you cannot change. But identity is such a fluid thing that I am loath to tell my young son outright that he can never be a girl and that it is wrong to think he can. If tomboys are accepted, why not - I'm making this up here - jill-girls?

Back at bedtime with Lucien: "I'm a general!" he announced later. "I have a tail!"

"That's nice," I replied. "Is it long?"

"Yessss," he wavered - I could hear his brain working in the dark, trying to decide how long this imaginary appendage should be.

Then, he exclaimed, to the slight alarm of his Dad sleeping on the other side: "Ouch, Papa, you're squashing my tail!"

Hmm. Boys will also sometimes be small animals, it seems.

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