Just A Quick Queery

This is the third grow I've started and the advice I've picked up has been invaluable indeed! I have just germinated a few seeds four Northern Lights and four Chrystal(White lightening) they are 12 days old today and I noticed one of the seeds has a second stem starting to grow from it. I was just curious if anyone had any advice on whether I should nip it off or just leave it to grow and see what happens which I must admit I am quite tempted to leave it and see what happens.
I have included a couple of photos and would appreciate any feedback you may have.

Looks like a new seedling, sure there's not two seeds there?

Ive read about this before somewhere. I think its a mutation where there are two seedlings started from the one seed. The little one will always be weaker and it will take from the bigger plant nutrient and room for root mass. I'd snip at ground level not pluck it. But if you wanted to let it go then go for it. Thats how you get great growing experience and then next time some one poses this question you'll have an answer for them!

It was definitely just one seed, I'll leave it for now out of curiosity as id only wanted six plants so I'd germinated a couple extra to make sure I got the required amount. Here is a pic of them at 19 days, I'm pleased with their progress!