Sibling Rivalry.... Perhaps

My 13 y/o son Micheal doesn’t think his 3 month old brother Messiah likes him and I think he’s starting to get really frustrated.

Messiah cries real tears whenever Micheal picks him up for longer than 5 minutes. If I leave them for 10 minutes to just shower I come out to Messiah red and face wet with tears. Micheal will say “Why doesn’t he like me” or “When will he start liking me” and at first I didn’t think much of it until Messiah scared his big brother to tears. Literally.

I don’t know why my baby does this and Micheal is such a wonderful big brother. How do I help my oldest to not feel as if baby doesn’t like him?