Danny and Liam Poole went missing after travelling in Malaga in 2019 and, in 2022, the investigation into their disappearance was turned into a murder probe.
A man in his 30s from West Sussex and another man in his 40s from the Merseyside area have now both been arrested on suspicion of the alleged murders.
They have been questioned and released under investigation pending further enquiries.
Danny and Liam, from Burgess Hill, hired a car, a grey Peugeot 308 with registration 0254 KTM, when they arrived in Spain on March 31 in 2019. However, the vehicle was never returned to the car hire firm and was later found abandoned by Spanish police.
The pair’s luggage was left in their hotel together with their passports, suggesting this was not a planned disappearance.
Spanish police took primacy of the investigation, and the Surrey and Sussex Police Major Crime Team worked closely with them to try and find 46-year-old Danny and 22-year-old Liam.
The circumstances surrounding their disappearance remained under close review and a decision to treat their disappearance as a murder investigation was made by Sussex Police in 2022.
Legal steps have now been taken to allow the Surrey and Sussex Police Major Crime Team to lead the investigation, taking over primacy from the Spanish police.
Danny and Liam’s families have been updated and echoed the force’s calls for anyone with information to come forward.
Detectives are continuing to appeal for witnesses to the case and the force is offering a £10,000 reward for information leading to the arrest and charge of any person responsible for Danny and Liam’s disappearance.
Simon Dunn, detective chief inspector, said: “Although Danny and Liam went missing in Spain, we believe there are people in the UK who may hold vital information about their disappearance.
“We understand there may be some who have felt unable to come forward before now, but it’s not too late to do the right thing.
“Whether it’s something you know, or something you may have subsequently heard, we urge you to get in touch and share it with us.
“We will listen and we will investigate any viable new lines of enquiry.
“You may not appreciate the importance of the information you have, but it could be the piece of the puzzle we need to build the picture of what happened to Danny and Liam.
“Even the smallest detail could be significant in helping us provide their families with the answers they so desperately need and deserve.
“Information can passed to police directly via the online Major Incident Public Portal. You can also call 101 quoting Operation Pheasant, or report anonymously via the independent charity Crimestoppers on 0800 555 111.”
