Family ties did not stop Lee Bowyer delivering another painful blow at the end of a difficult week for ailing West Ham. The 32-year-old east Londoner is from a family of Hammers supporters but it was his goal seven minutes into the second half that left his former club in the bottom three of the Premier League.
It gave Birmingham a fourth consecutive victory and a run of seven unbeaten to defend at home to Blackburn on Tuesday, when they will be confident of maintaining their unaccustomed proximity to the leading group. West Ham go to Bolton the same evening for a fixture, even at this stage of the season, that will be labelled a six-pointer.
Bowyer's goal, capping the latest in a series of excellent displays in his attacking midfield role, was particularly uncomfortable for Gianfranco Zola, for whom he made only six appearances before he was allowed to switch to St Andrew's on loan last January in a move that became permanent at the beginning of this season, with no transfer fee involved.
"It does not surprise me that he is playing such a key role at Birmingham and I'm pleased for him that he is being successful," Zola said. "But when he left West Ham it was at a time when he was coming back from injury, was not playing regularly and needed games.
"The financial situation did not help when the move was made permanent but there were other reasons for letting him go. The possibility for him to play regularly was not there with us."
His current manager does not underestimate the bargain he acquired when Bowyer opted to stay in the Midlands. "I don't know what price you would put on him now," Alex McLeish said. "I knew he had quality and sometimes it just needs the right atmosphere for a player to shine and I know things were not right for him at West Ham.
"But he has succeeded my expectations. He loves the atmosphere in the dressing room and the training ground here and it has given him a new lease of life."
Birmingham probably should have scored more goals. Cameron Jerome, denied by Rob Green in the fourth minute, headed a good chance over the bar just before half-time. After the break, Liam Ridgewell knocked the ball over the bar when it looked easier to score and Christian Benitez, clear after Julien Faubert's stumble, dragged his shot wide.
Nonetheless, there were reasons for West Ham to feel they are not enjoying the best of luck. In the week in which Dean Ashton, the striker in whom Zola had such high hopes, reached the sad end of an agonising line in his ultimately doomed battle to continue his career, his team's shortcomings up front were again uncomfortably visible, although their Italian forward, Alessandro Diamanti, had a frustrating afternoon.
Having gone within inches, twice, of sneaking shots the right side of the posts in the first half, he went close twice more in the second half before the sight of a curled free kick bending away late as West Ham gamely chased an equaliser proved just too much for him, causing him to tear open the front of his shirt.
To make matters worse, Zola's side had Mark Noble sent off with 12 minutes left after referee Lee Mason booked him twice in six minutes, the first time for dissent, the second for a tackle from behind.
Zola had not cared for Mason's performance even before that. "Referees are human and make mistakes but he made too many today," he said. "And I didn't like the way he reacted when some of my players complained at the end. We had a right to complain."
Referee: Lee Mason
Man of the match: Bowyer
Match rating: 5/10