It's rare even when it's close together. There's something like 11 recorded cases of it ever happening. You would have to be one of the very special few women who continue ovulating even when pregnant. & even then, our bodies thicken the uterus lining so a second embryo can't attach itself. It's also like you said, usually 2/3 weeks apart as then the babies act like twins and there's not much threat to the younger one. 11 weeks apart the second baby would be born at 29 weeks and that's assuming you made it to 40 weeks. I think one of the cases were 8 weeks apart.
I'm rambling lol, but yeah, I don't think it's likely at all! x