Yes, the form Jonahs' is the possessive form of the plural noun Jonahs.
The singular possessive form is Jonah's.
EXAMPLES
singular possessive: Mr. Jonah's house is on the corner.
plural possessive: The Jonahs' house is on the corner.
no he has a man
Lucien Laviscount
To be the next holder of the memories.
Their show
kevin, nick,and joe
Skidmore
Ectoplasm.
Jonah was wrapped in the belly of a big fish.
Lucien Laviscount
Howard
Yes I like Nick jonas
I don't know for sure but I think so.