It totally depends on the personalities of the kids, and the age differences, etc.
I was an only child for 6 years.
Then my LOOOONG awaited siter was born. Mom and Dad had been wanting more kids for years. Naturally they were beyond ecstatic to have another. Naturally this in addition to the adjustment of not being the only child anymore made this difficult for me as a 6yo. My second sister was born 18 months later (talk about a surprise! the doctors had told my parents they would never have ANY more kids and I was a miracle...) when I was 7.
Due to the age differences we had almost nothing in common, and I didn't get along that great with my sisters. They got along FABULOUS with each other though.
My baby brother was born when I was 15, and I got married when he was 5. Now he's a teenager and of course he doesn't really have any interest in much I have to say. From the time I was 7 until the time I was 15 we were a 3 child family, so that was a large part of my growing up years.
Anyways, due to personality differences, I don't have a lot in common with my first sister, though we get along a LOT better than we did when she was 5 LOL!
My second sister and I get along really well, but we have more in common. She had her first baby at home, she wears slings, doesn't vaccinate, and so we have those in common too.
I do not believe there is anything inherent in a 3 child family that makes it "better" or "worse" than 2 children or 4 children. Of course I have five children living with me so obviously I like the big family deal LOL!