Iv been told Jacobs can be bred from the first year, so they will give birth when they're just 1..is that correct?
As someone else mentioned, a lot of larger / commercial breeds will lamb as hoggs, ie., at 13 months old.
However, we are commercial sheep farmers and rarely lamb any hoggs. It's just too much extra work; they've no idea what they are doing and are too flighty and silly to settle to the job, and we don't have the spare time at that time of year to help them.
So in your situation, first-time sheepkeepers, where the sheep are primarily pets/lawnmowers, I would absolutely not countenance tupping my ewe lambs. Give yourselves a year to get to know them, and them another year to grow and settle.
And if you can arrange to go and help out at with a local flock at lambing time next year, that experience will be priceless