No they are not. They are both Indo-European but each is from a completely different branch of the Indo-European languages. Latin stems from the Romance branch, while Greek from the Hellenic branch. Other than their common “ancestor” language group, the only other similarity I can think of/find right now is that Latin did borrow many Greek words due to the Roman’s heavy influence from Hellenic culture. However, this doesn’t mean that they are at all related.
Greek itself has myriads of Turkish words due to the Ottoman occupation of the Greek lands (Greece as a nation state did not exist yet at this point if I’m not mistaken) from 1453 until 1821(almost 400 years), however it would be ridiculous to make the claim that Greek and Turkish are related, given that Turkish is an Anatolian language which only shares commonality with Greek due to the fact that they are both Indo-European branch families. Hence, it is ridiculous to make the claim that Latin is related to Greek simply because they borrowed many words.
So, linguistically speaking both Greek and Latin are from majorly different language families, and we have discussed how you can’t make the claim two languages are related simply because they borrow words from each other because of various political/historical reasons.