Three times Chuck Bass has cried 
When his father died (2.13)When his mother told him she wasn’t his real mother (3.16)When Blair told him he wasn’t the father of her baby (5.03)
You can tell how much family is important to him. He also almost cried in 4.02 when Blair told him she didn’t love him anymore, and in 4.22 when he was letting her go. This shows how much he also has always wanted her to be part of his own family.