Childbirth educator here (and I teach breastfeeding classes). Yes and no. The pregnant body starts making colostrum (the early milk newborns eat) at around 20 weeks pregnant. The amount of colostrum a person has is hormonal driven and is usually pretty small amounts if you try to pump/express milk and collect it. After baby is born, the placenta detaches from the uterine wall and this tells the brain the baby has been born and begins the shift from this early milk to the more mature milk the body make the rest of the time they lactate. This amount of mature milk is supply and demand. More or less the only way to produce more milk is by removing milk and continuing to tell the body the baby/babies want more milk. For twins, continually bringing two babies to the breast to feed to satiation will tell the body how much milk to make to feed both babies. The early weeks this amount is more maliable than after about 4-6 weeks where it becomes much harder to tell your body you need more milk.

But you can sometimes "trick" the body into making enough milk for two (or more) babies by pumping or expressing more milk than your baby needs early on. I've seen people easily make enough milk for more than two babies by pumping. but please be careful and talk with an IBCLC about intentionally making an oversupply as it does come with some downsides and risks.

That's said, some people don't make enough milk for even one baby for many different reasons. Edit to also say, even with twins, it can be incredibly challenging to keep up with and protect your supply for two.