All three types of joint account holders are usually close to the primary account holder, including old friends and family members. (lendedu.com)
Some banks limit joint accounts with minors to those ages 14 and older. (sapling.com)
If you're splitting up having lived together, money you have in joint accounts for household bills or similar would be assumed to belong to both of you in equal shares. (moneyadviceservice.org.uk)