I don't understand why this shocks people so much. A seedlings first true leaves are often single or tri-bladed. Other leaves coming in are so small that you wouldn't be able to tell initially how many blades they will end up with. It is very likely that as a "tri-bladed" leaf grows up it will begin to show those two additional small blades. Some plants might even grow only three-bladed leaves its' entire life, or just plain start off mutant-looking.
And I just have to say, it kind of irritates me when people refer to a seedling as being their "baby" or their "babies". Too many people do it and it is freaking ridiculous.
"Look at my
baaaby"..."What's wrong with my
babyyy?"..."I don't know what's up with my
babiiies"...
Jesus. These are not babies we are growing, they are fucking plants.