Answer:
Jill and Brad and Erin. -This sentence is an incomplete sentence first off, and it has no context.
Eli and Sam are brothers who have a lot of fun together. - This is a complete sentence.
The wind blew fiercely the rain fell steadily. - This sentence could use the conjunction word. Ex: The wind blew fiercely, and the rain fell steadily. With this I believe that this is good sentence.
Explanation:
My final conclusion is that Jill and Brad and Erin is a run-on sentence, and I also believe that the sentence "Eli and Sam are brothers who have a lot of fun together." could also pass as a run-off sentence.
So, if you needed help with this I really hope this helped you out. Please give me brainliest and have a great day or night! Thank you.