When? How young can you be
When - When you're with somebody that you trust 100% and you LOVE! When you say okay, and not when you feel uncomfortable or unsure. When you feel you're ready.
How young - Well, you can be any age but you should be at an age where you can make mature decisions to know if you are ready for something that emotional. That's why between 14 and 17 is usually the 'legal' age to which you are capable of making these decisions, although sometimes it could be as young as 13 and as old as 18 in some places. You can't go to jail or anything, but for other purposes they make those standards.
It is okay to have sex when you think you are really ready. When you can take up the responsibilites behind having sex such as having kids, having an std, or being used by someone just for sex.. THE BEST TIME TO HAVE SEX IS WHEN YOUR ABOUT TO GET MARRIED OR YOU ARE MARRIED... Or you no that you and that person will have a long lasting relationship but a couple months but some years.. I would advise anyone to keep there virginity... It is to precious to just give to anyone.. I would say 17 or older if you want me to put an age to it.
Personally, I don't think it matters as much that you're in love. Not saying to be a slut or anything. But I think what matters is that your mental state will be able to handle it. Some people could get really hurt and torn apart by it, and they may think that they're in love when they aren't, and spiral into other complicated emotions. So if you're thinking about doing it, make sure that you're looking out for yourself. Mentally and physically.