The phrase 'time twins' is simply a shortened way of saying two children born in the same location and very close together in time. This will have become more common in the West in the last century, as more births are now in Hospital, rather than at home. By having births concentrated, it makes it far more likley that two or more will occur together, ie within minutes and yards of each other.

The only time realistic way this would occur outside of hospital is with real twins, and the whole point of time twins to see look for similarities due to their birth charts,not due to them being brough up together.

Nothing to do with soul mates or such like.