Question

find the relative clause. if it is nonrestrictive, set it off with commas. if it is restrictive, submit the text without making any changes. when we were kids, my eldest brother whose imagination knew no limits would entertain us for hours with his fanciful stories.

Explanation:

A relative - clause modifies a noun. "Whose imagination knew no limits" modifies "my eldest brother". It is a restrictive relative - clause as it is essential to identify which brother is being referred to.

Answer:

When we were kids, my eldest brother whose imagination knew no limits would entertain us for hours with his fanciful stories.