The game was finely balanced with the scores locked at 4-4 when a mass brawl erupted on the hour following a high tackle on St Helens captain Paul Wellens. Referee James Child's response was to hand Cross a red card and send Widnes captain Jon Clarke to the sin bin and Saints took full advantage to seal victory with the aid of tries by Lee Gaskell and Francis Meli.
Widnes gave a debut to England forward Gareth Hock, who has joined them on loan from Wigan, while Saints were forced to cope without injured England hooker James Roby.
St Helens, who were looking to bounce back from a humiliating 40-4 home defeat by Huddersfield, also lost prop Josh Perry after only five minutes, following a crunching tackle by Hep Cahill, leaving Brown with the use of just three substitutes for the rest of the match.
It looked a costly blow for an hour as Widnes matched their visitors blow for blow as they went in search of their first derby victory since securing a 20-17 triumph in the old Stones Bitter Championship in April 1994.
The Vikings made the best possible start, taking the lead after only five minutes when winger Paddy Flynn palmed back Joe Mellor's precision kick to the corner for centre Stefan Marsh to touch down. Saints' only try of the half came from winger Meli, who took Wellens' long pass to cross on 17 minutes.
Saints spurned the chance to take the lead just before the interval, running a penalty from in front of the posts, while Widnes goalkicker Rhys Hanbury was wide with an ambitious penalty from the halfway line.
With the game finely balanced, Widnes were suddenly reduced to 11 men on the hour when Cross was dismissed and Clarke sin-binned following a brawl involving all 26 players.
Not only with a two-man advantage, Saints were boosted by the return of the injured Jonny Lomax and they went on to dominate the final quarter. Wellens was thrown back from the line but the Vikings were clearly short of numbers when stand-off Gaskell went through a gap for Saints' second try on 67 minutes.
Gaskell converted his own try and Saints made sure of the win nine minutes from the end when Lomax seized on a loose ball 20 metres out from the Widnes line and sent Meli over for his second try, with Gaskell kicking a second goal.