DVC wouldn't allow it. I have my 20 yo D on contract (19 @ time of purchase) but was not able to include my 16 yo (15 @ time of purchase). They required a copy of our IDs for age verification.
It is actually one of the reasons I haven't added on yet. I want both kids on the deeds but I don't want to deal with the BS of adding names on multiple contracts. I feel like I need to wait to add on until after my 16 yo turns 18 so I will only have 1 deed to modify.... unless I want to have separate memberships... ugh.