A taxi driver accused of killing his wife and three young children found text messages from his wife's lover on her mobile phone, a court has heard.
Rahan Arshad denies four counts of murder
Rahan Arshad, 36, showed the "love messages" on his wife Uzma Rahan's phone to her brother Rahat Ali, 27, Manchester Crown Court heard.
Mr Ali said he was shown the messages as proof Uzma was having an affair.
Mr Arshad denies murdering his wife and three children at the family home in Cheadle Hulme, Manchester, in July.
A friend of Mrs Arshad, Humma Jauhaur, also told the court that Mrs Ashad had complained that she never felt safe with Rahan Arshad.
Asked about their relationship Ms Jauhaur said: "He was always accusing her of flirting with other men. He would always say,'That guy is looking at you. What are you looking at him for?'. He was jealous when any other men looked at her."
Mr Arshad is accused of repeatedly clubbing Mrs Rahan, 32, and their sons Adam, 11, and Abbas, eight, and daughter Henna, six, with a rounders bat.
Their bodies lay undiscovered for almost a month.
The family's bodies lay undiscovered for almost a month
Mrs Rahan's partially-clothed body was found in the master bedroom. The three children were found in the lounge, which was infested with bluebottles and maggots.
The couple had an arranged marriage in 1992 and Mrs Rahan moved from Pakistan to Manchester to live with Mr Arshad.
Mr Ali said the couple had a turbulent relationship with frequent rows.
Taxi driver Mr Ali said Mr Arshad visited him at his Birmingham home in 2003 and showed him a mobile phone with romantic messages from Mrs Rahan's lover, known as Nikki.
Asked the type of messages, Mr Ali replied: "You can say love messages."
He said Mr Arshad's behaviour changed when he discovered the affair.
Previously he had liked his wife to dress in Western-style clothes - he then told her she must dress more traditionally.
The case continues.