Why is the Latin relative pronoun so alike the interrogative "quis, quæ, quid"?

Latin Learning Latin
1

Hello!

Both pronouns are very similar, only differing in nominative, if masculine or neuter, and in accusative, if neuter, though their meanings don’t seem to relate (e.g.: while in Quae est illa? the interrogative quae is exactly the same as the relative in feminine nominative, I can’t see any similarity between this quae and that quae that justifies such similar forms). What am I missing?

2

The short answer is that it’s a small mental step from interrogative qu- to relative use. Same in English of course. “Whom do I love?” quem amo? > “The man whom I do love” (is) quem amo.

3

Thanks!