Well we actually have 8 people, My hubby and I and our 6 kids...no babies, all KIDS...
Oh and did I send you a message with the link to my PTR today..I swear I can't remember!
Edited to Add: Are you going with Make a Wish?? Or another organization? If it is not MAW...? Then I don't know how they would handle all of this??
Since you already have eight people, GKTW has been known to assign you TWO villas. So...there would be plenty of room. They won't make any of the official MAW approved guests stay at a different place.
However, it is up to them if they allow an
extra person to stay onsite.
I have seen multiple trips where they have allowed folks to stay onsite (this has included a set of grandparents, aunts, family friends) and I don't really remember one where they haven't...except in cases where the villa was full with 7 people and they could not add more. But since you will have two villas - you should be good to go.
Then it is up to MAW whether to make him an official part of the wish.
If you had 6 younger kids, I think it would be likely they would approve him...but since you have older kids (that can theoretically be on their own) then they may not count toward the "kid" number and may even be counted as "adults"...anyone over 9 is an adult at Disney anyway.
I was allowed to accompany Lauren's family as an official part of their wish - I am more of a family friend than anything else - but several factors made that a necessity...They have other medical needs in the family, they never travel without me (or another CNA if I can't go) because of the other medical needs, and I was an official CNA approved by Medicaid to meet Lauren's needs. Not sure which of those things allowed me to go, but MAW did pay for all of my expenses and I was an official part of their wish. They only have 2 children, but their other child has medical issues, her father is a severe brittle diabetic and Lauren is a quadraplegic that requires a lot of care.
Each state is different. I know that can be frustrating, but I completely understand it because they each have their own board of directors, separate budget considerations and are independent of each other - so each of them have different policies. Money also plays a role - if they are tight, they may be less likely to approve an extra person if the need is not clearly established.
There have been issues with children in the process of adopting going with the family, too, with a few states.