Parents grossly exaggerate how little attention the second child gets.
This weekend my eldest wanted to play chess. No problem. My preschooler is < sarcasm > totally self sufficient and willing to play by himself while I give his older brother fifteen minutes of attention. < /sarcasm > Not because I ignore him, but because he knows what he wants in life and isn’t afraid to just go out and get it.

Image credit: Ken Teegardin via Creative Commons share alike
Peanut and I set up the pieces. And four-year-old Butterbean grabbed his stickers and started an art project.
On my shirt.
I, of course, supported his artistic drive. Mostly because it allowed about five minutes of play.
But at one point he pushed a stick hard on my back, and it hurt.
“Ow,” I said. “Please stop.”
“Why?”
“Because that hurt.”
“What part?”
“The part where you just pushed on my back.”
“Let me see.”
He lifted the back of my shirt and went looking, until he found what he said was a “red hurt spot.”
I made interested sounds. Not because I was ignoring. Because I couldn’t finagle my bishop into position.
Butter went to his room for his doctor kit, which he wielded expertly on my medical emergency. The red spot got fake injected, fake temperature checked, fake examined, and fake reflex checked.
And it got redder, he noted.
Science.
Ad Peanut and I got into the middle of the game, Butter went upstairs to get his geology tools: hammer, pick, tweezers, brush. All plastic, thankfully.
And declared he was a paleontologist. And started to dig into my back.
“Ow. Please stop it. That hurts.”
“Mommy, it’s okay. I’m a paleontologist.”
“Paleontologists look for fossils. In dirt. Not blood in their Moms.”
“Mom, it’s okay.”
“Yeah, well, still hurts.”
“Mom. Really. Okay. It’s O. Kay.”
He ditched the rockhound tools and picked up the queen my knight had just taken.
He used the queen to back methodically on the red spot on my back.
“Still red.”
Again with science.
“Yes. That’s the blood trying to help the skin get better from a hurt.”
“What hurts?”
“Banging queens on my back.”
“Mommy, I’m not banging queens on your back. I’m using one queen to find clues. Remember? I’m a paleontologist.”
I chased down Peanut’s King and ended the game just before the little one drew blood.
You see? Having two is totally easy. You should have several. Not much harder than having one. Or none. Or a puppy. Or a sandwich.
The broader point is that second children aren’t ignored. They don’t suffer from lack of attention. They have a better sense of what they want from life and seek without hanging back, without waiting for permission.
We could all learn from my youngest. If you want something, don’t let anything stand in your way. Not reality, or physics, or the medical needs of your mother.