What drawbacks can I expect from keeping two twin seeds?

They will complete for resources and space in the root zone, one of them will likely be more dominate and the other dwarfed. Not to say that is 100% they could be equal but he odds are not in your favor. Most people just pluck off the weaker looking one in a weeks time and go with one strong plant per pot. Its your planting adventure though so do what YOU want vs what others say :)

i had that from some superstaiva seeds, in one run 10 seeds and 12 plants, i separated them early and got well growing plants 12 out of 10 seeds, nice

More likely than not, one will grow substantial faster than the other and shade out/stunt it's sibling. Predicting outcomes is honestly a crap shoot with "normal" genetics, mutations lend a curve ball all of their own.

You may have to expect growth being a little bit slower and not getting as much yield out of it, unless you plant them in a really big container where their roots will not compete for available soil... But i am supporting experiments, so ´give her as much soil as possible and go for it! Good luck! 😉

I said something stupid, one of the two is a clone of the mother, they are not twins 😉

All twins I have grown have been either hermaphrodites, flowered really weirdly/poorly.............or both. These days, any twins I get, get the chop as soon as they are "born", I don't want to waste my time and space growing hopefully maybes!

It's an interesting mutation, it's called polyembryonia. There are two embryos in a seed, it can happen even with 3 but it's very rare. You will have one of the two plants that will be slightly smaller than the other. But genetically they are twins. It's going to be very interesting to follow 😉✌️