Mark Brennan was born in about 1981 to Russell Brennan and Fay Brennan. He had a younger brother Tyler Brennan, another brother Aaron Brennan and a sister. He was studying in 2000. Brennan attended police training college and later became a police officer.
Detective Mark Brennan was first seen as a detactive in the investigation of the Who Pushed PR storyline, in which Paul Robinson was pushed from the mezzanine. Brennan suspected Rebecca Robinson but she had an alibi. Brennan dated Kate Ramsay. Brennan says he has to solve Paul's case to prove himself to his superiors but in the end sees his relationship with Kate as more important. Due to trying to bring down corrupt police officer Wes Holland, and arresting him, Mark is targeted with small acts of revenge for arresting Holland. Things escalate and Mark is asked to go into witness protection until the trial. Mark asks Kate to go with him and she agrees. However, she misses the deadline and Mark leaves without her in 2011.
Brennan returned to Erinsborough in 2013, saying Wes Holland had died, shot dead by police when he was fighting with him. This meant Mark Brennan could return safely to Erinsborough. Brennan moved back to Erinsborough and rejoined the local police.
In early 2014, Brennan helped Paul Robinson find the killer of Kate Ramsay. Brennan then began dating Paige Smith who was 13 years his junior. SHe moved in with him at No 24 Ramsay Street. Brennan set himself up as a mechanic but being an ex copper, he was often seen to for advice when other Ramsay Street residents had problems. Paige and Brennan split up when he let Dakota Davies touch his chest. Brennan later decided he did not have feelings for Paige when she wanted to get back together but had seen him kiss another girl.
In February 2015, Brennan told Matt Turner he wanted to re join the police force. He was told he would have to rejoin as a constable rather than a detective. Brennan started dating Naomi Canning. In April 2015 he had Nick Petrides arrested for doctoring Paul Robinson's tests results so he could have a cancer centre built. Brennan and Naomi are having an on off relationship. In May 2015, Paige Smith still admitted she had feelings for him. The following moth she kissed him. She is still debating over whether she loves him or not. Brennan holds a candle for Naomi.
In July 2015, Brennan's father Russell arrived in Erinsborough. It soon transpired that Russell used to beat up Tyler when Tyler was 10 years old. Brennan told Russell to leave and Russell called off his relationship with Sheila Canning. Brennan and Paige soon got back together yet again. In September 2015, Paige was friendly with Tyler. Brennan said to Paige he wanted to have children. Mark and Paige got engaged. Paige was later kidnapped and was knocked down by her kidnappers car when she had escaped but luckily Mark was standing on the top of the road Paige was hit by a car on . Mark runs to her side and is once again confronted with losing someone like he lost kate. Paige is taken to hospital and Mark leaves the hospital to work after Karl gave Mark Paige's ring and he had a flashback to when Kate died and he was given back her ring. Mark later returns to the hospital and tells Paige she has to marry him as soon as possible.
However, Paige is dumped by Brennan on the day of the wedding when he finds she was lying to him yet again and was involved in the Dennis Dimato scandal with Michelle. They both decided to end their relationship. Brennan begun dating Stephanie Scully. This initially made Paige jealous, especially when she came to visit Steph and apologise to her after an altercation in The Waterhole and Paige saw a topless Brennan.
In the wake of the Lassiters explosion in March 2016, Paul Robinson was a chief suspect and Brennan was convinced he was guilty. Steph said he may be innocent. Brennan was later taken off the case. When Steph was being stalked, Brennan contravened police procedures and was suspended. He later apprehended her stalker but was stabbed in the chest.
In September 2017, Mark found out that Tyler was only his half brother as Fay had an affair with Hamish Roche. This meant Tyler was only the half sibling of Aaron and Chloe as well. Hamish was in debt so after he was contacted, he visited Erinsborough and Tyler bonded with him, his real father. Hamish owed millions of dollars and wanted to take Tyler away. Hamish started to do devious things but befriended people, only to take them for a ride. Mark was onto Hamish and Hamish even reported Mark to his superiors for harassment.
In November 2017, Hamish was found dead in a spa. Tyler admitted that he had hit Hamish on the head with a small ornament but Mark was sure that Tyler did not kill Hamish. Mark even covered up for Tyler. It soon transpired that Brennan had done this over the Sonya Rebecchi case. Det. Bill Graves said this is the second of 2 complaints against Mark. Brennan was suspended due to evidence of him tampering with a crime scene. He was then the chief suspect in the Hamish Roche murder.
Full Name: Mark Brennan
Mark is known by his surname Brennan to his friends.
Some viewers wonder if Mark Brennan is related to Beth Brennan who lived in Ramsay Street from 1992 to 1993 due to the same surname. But this is highly unlikely as Mark has never mentioned he is a cousin of Beth to Brad Willis, who was Beth's husband for a short time. Also when Ned Willis arrived, Brad and Beths son, so far he has not said to Mark that he is the son of Beth and therefore related to him. To confirm there is no relation in May 2016, Beth was mentioned to Mark by Brad when he was discussing Ned to him and there ws no mention that she was a relative of Mark's so it is just a surname coincidence and Brennan is quite a common name.
Father Russell Brennan
Mother Fay Brennan
Children - Caitlin Brennan (died during pregnancy)