The body of Aaron Armstrong, 25, is said to have been discovered at a house in Blyth, Northumberland, on Tuesday.
A family friend told the Sun they were "absolutely gutted" about Aaron's death, so soon after Sophie's.
Confirming Mr Armstrong's death, Northumbria Police said: "There is not believed to be any third party involvement and a report will now be prepared for the coroner".
"She had suffered from depression and anxiety and there was talk of financial issues which obviously adds to the worry she was enduring".
Friends and family gathered to pay their respects at Sophie's funeral at St George's Church in Jesmond, Newcastle on Thursday 5 July.
On Monday, he had posted an emotional tribute to his girlfriend on Instagram.
ANP leader Haroon Bilour among 12 killed in Peshawar blast, police say
Local television channels broadcast live scenes of ambulances arriving at the site and rushing victims to the hospital. Bilour's father, Bashir Ahmed Bilour, was killed by a suicide bomber during a meeting in 2012 ahead of the election.
Posting a picture of the two of them together, he wrote: "I will never forget that smile I love you so so much baby your my world forever ever and always".
Following her passing, Armstrong had expressed tremendous grief on social media.
An inquest has been opened and adjourned into the death of the former Love Island contestant.
Sharing a picture of the order of service, he wrote: 'I love you with all my heart my handsome angel I'm absolutely heartbroken I can't stop crying and I can feel your spirit in my soul RIP Sophie Hannah Gradon'.
"You really don't know the battles they go through every single day". I'm heartbroken for you soph to have felt this pain.
Tributes on his Facebook page read: 'You can be with her now.R.I.P Aaron'.
Readers seeking support and information about suicide prevention can contact Lifeline on 13 11 14, Suicide Call Back Service 1300 659 467 or Kids Helpline on 1800 551 800.