Actually it is somewhat common with many plants. it is usually the result of fused seeds or fused stems in high humidity. It poses no threat to the plant or its future.

Dave

I've even heard that some tricot Solanaceae plants can have advantages over their dicot siblings. I'm not sure about citrus. I might be thinking of a different kind of tricot, though.

Are you sure that's three cotyledons you're looking at? The two at the base in the picture appear to be cotyledons. Those upper leaves just look like leaves.

Shule - Well its weird because the other one that I grew looks normal - stem with 2 cotyledons. I have no idea what this little guy is doing though lol

But they are definitely joined at the same place on the stem.

Yeah digdirt2- Maybe they fused or something. I put them in a 5 gallon bucket lined with aluminum and 2x1500lm led lights hanging from the lid. So maybe the heat and the moisture from the soil caused them to fuse. So strange haha. Learn something new everyday. I was really hoping though that there would be 2 seedlings emerging.