Ways for little man to learn to sit up!?
(I have a sit me up chair, he sits in his high chair, I have a Boppy)
Practice sitting him up with as little as possible. Just a boppy or pillow behind him. Using a chair too early won't teach him to use proper muscles. Just sit him up little amounts of time everyday and before you know it he'll be sitting.
He sits up on the couch a lot