When my sister and I were little, we’d play Doctor when the folks weren’t around. “Stay on your back, mister,” she’d order. “You’ve been in a serious accident,” checking my tummy with a rubber spatula.

“You need a physical,” as she undid my belt, both of us giggling, and proceeded to do tests. Then we’d switch, the difference being that she could make me grow. Siblings cooperate when they’re having fun, especially a type of fun they don’t wish their folks to know about.

Our folks made us take piano lessons. As my sister was the better note-reader and I, at figuring out from listening, duets let us cover each other’s shortcomings.

Truth be told, however, we liked playing duets for another reason. Rather than one of us on the upper register and the other on the lower -- how duets are supposed to work -- we’d do it with my left thumping the bass, her left catching the next span, my right next higher and then her right adding the fluff at the top. Mistakes could always be blamed on the other.

But as we couldn’t pass off a glissando in mid-point, we have to decide whose arm went over whose. By the time I was an octave above middle C and she was an octave below, I’d be on her boob, but she didn’t mind because that’s how we did it. Or she’d sit on my lap for four-hand duets, me doing the bottom and top, her, the middle. Or sometimes I’d sit on hers while she reached around.

As I said earlier, siblings cooperate when it’s to their mutual benefit.

Once when we were in Iowa she dared me to go skinny-dipping. We could undress separated by a bush and stay under water, she said, but when we were paddling around, I still saw.

I knew it was a trick, her “Help! Help! I’m drowning!” but she knew I knew it was a trick, so it wasn’t really. I saved her with the cross-chest in Lifesaving, and she bumped against my cock. We went back to our sides of the bush to redress and sat in the sun until our hair dried. Cooperation.

But without a bit of rivalry, siblings would end up being boring to each other.

Maybe we’d wrestle around, and if her top slipped up and nobody else was around, she’d say it didn’t matter. She’d get between my legs, but I’d never let her stay. Sometimes we’d just roll over and over each other, back and forth across the living room rug, over and over, our hands everywhere.

Another example: my sister would get videos, foreign ones, and hop onto my lap and pull my arms around her stomach. When I’d look down -- she could tell I was without even turning her head -- I could see her bra. Not that I didn’t see it around the house, but this was her doing.

When the movie got to a hot scene, she’d stick her hands behind her head to cover my eyes. “Can’t look,” and let me feel her breasts. Again, it wasn’t as if we didn’t bump into each other all the time, anyway, but this was her doing.

So why’d she do that? To make me get a boner that she could sit on.

My brother slips into my room without knocking and closes the door. Even in the darkness, I can tell he’s in his underpants.

“What are you doing? Get out!” pulling up my sheet. He can’t come just barging in when I’m, well, when I’m doing something.

“Shush, or they’ll hear,” plugging the crack beneath the door with the rug and plopping himself down beside me, me of course stopping what I’m doing.