Question

what happens when 2 helium fuse in the sun

Answer 1

Two helium will not fuse in the sun, not until most hydrogen is consumed. This is because Hydrogen will fuse at temperatures lower than that required by helium. So, for Helium to fuse, most Hydrogen must complete its fusion first.

After that , helium will start fusing. Now, generally, 2 Helium will not fuse. They can fuse to form Beryllium, but it is uncommon. This is because of nuclear instabilities and binding energy differences, which you will learn in higher classes.

Generally, three helium fuse into carbon. At this same time, some helium will fuse with that carbon to produce oxygen. This can go on and on.