The pair, named locally as Ryan Theobald, 21 and Janis Kozlovskis, 17, both died after an attack in Silver Street which has seen detectives launch a double murder probe.
A third victim, an 18-year-old boy, is recovering after being taken to hospital with stab wounds.
A 17-year-old boy has been arrested and remains in custody over all three attacks.
The family of Janis have paid an emotional tribute, while cash is pouring into funeral funds set up for both of the pair in the wake of the tragedy in the early hours of Saturday morning.
Sister Russanda Kozlovska wrote: “I’ve just lost my little 17-year old brother to knife crime in my own home city of Doncaster.
“We’re all heartbroken - I've always seen things like this on the news but now it’s happen to my own family. My heart goes out to the other people who have lost there loved ones over knife crime.
“Janis went out on a Friday night in Doncaster. After their night out with his friends an altercation broke out and Janis and one of his friends Ryan Theobald has sadly passed away - he was only 21, both young lads with their whole life ahead of them – any help will go a long way.”
Meanwhile, a funeral fund has also been set up for Ryan.
Sharing the funding page, Alisha Samba wrote: “Ryan was loved by so many, he was such a funny, loving and kind hearted young lad.
"Ryan was on a night out on Friday night and ended up in a altercation which has ended up with him and his friend Janis losing their lives to knife crime.
“This heartbreaking tragedy has left his poor mum and sister absolutely heart broken. Let's raise some money to help give him the send off he deserves.
“Every penny will help.”
South Yorkshire Police were called to Silver Street shortly after 2.30am on Saturday, January 29.
Ryan was pronounced dead at the scene while Janis died in hospital after being rushed there by ambulance.