If the younger one is more mature and ready... it is not fair for that child to always be... in the older child's shadow.
This is not doing, that younger child a favor.
They do not have to go to Kinder, the same time.
They should be in separate classes, IF they do go at the same time.
Them going at the same time... should NOT be, the deciding factor, for both children. They are both, individuals... with different needs and development. So they should be treated as such. As 2 different individuals.
Is one child a boy and the other a girl?
That is what it seems like.
My Daughter entered Kinder at 4, then turned 5 shortly after.
SHE was ready. SHE wanted to go to Kinder. SHE was emotionally and academically ready. She thrived. She was not the 'youngest' one in Kinder, either.
Your oldest, will be entering Kinder, much older. You said this child is now 6.5 years old???????
Be aware, that in some schools, IF a child is 6 becoming 7, or 7 upon entering school... they will enter that child into FIRST GRADE. Not Kindergarten. Kinder is not 'mandatory' in many schools. BUT a parent can 'request' that their older child, enter Kinder, and they may make an exception.