Hi HundredPercent,
As I understand your post, your siblings are offering to put their payment information on your Apple ID, and you want to know if that's possible to do. You are able to use the payment information as long as it is valid, and you have the correct billing information. This is a very helpful option for parents of teenagers who want to pay for their purchases as well.
Payment methods you can use in the iTunes Store, Mac App Store, App Store, and iBooks Store - Apple Support
Thanks for using the Apple Support Communities!
Cheers,
Alex H.