Bendy:
Yes, you have fourth siblings.
Two brothers and two sisters.
Boris:
None.
You're the only one who Mickey adopted and you don't have biological siblings.
Cuphead:
None.
You are the only child in your rich family.
Mugman:
Yes, you have one little brother.
Felix:
None, You are the only child in your family
Oswald:
None, You are the only child in your family.