Williamstown confirmed the signing of Henty brothers Sam and Nick Murray on Sunday.
"Sam will bring great run out of defence," Williamstown general manager of football Stephen Soulsby said on the Seagulls' Facebook site.
"He's a daring, courageous defender in a similar nature to Brayden Monk, which has us really excited about our defensive side of the game.
"Nick is continuing to develop as a key tall and he can play at either end.
"To have the support of his brother both on and off-field will also be of great benefit and both are really excited to play at the same club in 2020."
He played 13 matches with Collingwood in 2018.
Nick split last season with GWS (NEAFL) and Wangaratta Rovers (O and M).
If the siblings nominate Rovers as a second club, they will be eligible to play if the Seagulls allow it.