Hi and welcome!
Your LOs are gorgeous!! Congrats on your new son!
Cluster feeding is basically feeding at shorter intervals before bedtime to try to ensure that your LO won't wake up hungry during the night (or at 5 weeks, won't wake up as often during the night to eat -- a little small to sleep the whole way through!).
Until my DD was about 8 weeks, she would feed during the day every 2-3 hours during the day -- as the evening wore on, she would want to eat every 1-2 hours. (As best as I can remember, I have such hazy memories of those early days LOL!)
Going by a 3 hour routine (which your DS may or may not be able to handle yet -- like I said, I think we were more on a hour routine at that age) -- if your DS woke for his first feed at 7 AM, he would eat at 7 AM, 10AM, 1PM, 4PM and then cluster feed at 6 PM and 8 PM with a dream feed at 10 PM. This would get my DD through until around 2-3 AM when she'd need to eat and then (hopefully) sleep until morning.
HTH!