My Eldest Brother Typically Makes Plans Last Minute

Hey everybody.

So I am a senior in HS and other brother (middle child) is a senior in college. Our eldest brother is married and lives close to us. My eldest brother tends to ask my brother and I to get together at his last minute when we’ve already made plans for the afternoon or evening. My (middle) brother and I both discussed that we appreciate him thinking of us, but we really need him to communicate plans at least a day in advanced because it sucks always having to cancel. Is there anyway to appropriately and respectfully communicate that to my eldest brother?

Any advice would help. Thank you!