Mason, 15, and Max, 16, died on the night of Saturday 27 January after being attacked in Knowle West.
Police officers and members of the public went to their aid but both died in hospital.
A 49-year-old woman and a 14-year-old boy have been arrested this morning and are in police custody.
A total of 12 people have now been arrested as part of the murder inquiry, including five individuals who have been charged.
Three people have been charged with murder and two people have been charged with assisting an offender. All have appeared in court and are remanded in custody.
Two boys, aged 14 and 17, who were arrested on suspicion of murder in the past few days remain in custody after warrants for further detention were granted.
Of the three other people arrested earlier this week, as previously stated, two have been released on conditional bail and a third released with no further action.
Detective Superintendent Gary Haskins said: “A dozen people have now been arrested since the tragic events in south Bristol last weekend.
“Mason and Max’s families are being supported by specialist family liaison officers and were earlier today updated about the latest two arrests.
“We are hugely grateful for the support the local community have shown us over the past week and we will continue to inform the public of any significant updates regarding this ongoing investigation.
“Five people have been charged with offences so far and therefore we would again remind the public not to share any images, footage or speculation about the incident so as to ensure those live court proceedings are not jeopardised.”
BRISTOL STABBINGS
- Cops arrive at Ilminster Avenue in Knowle West, Bristol, at around 11.20pm on Saturday, January 27 to reports of the stabbing.
- Victims are taken to to Southmead Hospital and Bristol Royal Hospital for Children after being found with stab wounds.
- The teens tragically passed away in the early hours of Sunday morning.
- Avon and Somerset Police launch a double murder investigation.
- A vigil attended by around 150 people is held near the scene on Sunday night.
- Max Dixon, 16, and Mason Rist, 15, are named as the victims as their families pay tribute.
- One woman recounts the tragedy of holding one boys in her arms as he lay dying.